Fluidized bed apparatus

Abstract

To provide a fluidized bed device that avoids generation of sulfur compounds and suppresses agglomeration of a fluid medium.SOLUTION: A fluidized bed device 100 comprises: a combustion furnace 110 that heats a fluid medium F having a particle size represented by a first particle size distribution; a cyclone 120 that separates a solid-gas mixture supplied from the combustion furnace 110 into solid matter having a particle size equal to or greater than a separation threshold below the most frequent value of the first particle size distribution, and solid matter having a particle size below the separation threshold and combustion exhaust gas EX; a connecting channel 130 connecting the cyclone 120 and the combustion furnace 110; a raw material supply part 150 that supplies a solid raw material R to the combustion furnace 110 or the connecting channel 130; and an inhibitor supply part 160 that supplies an inhibitor A that contains one or both of calcium and aluminum and at least a portion of which has the particle size below the separation threshold in the combustion furnace 110 into the connecting channel 130.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fluidized bed apparatus.

Background Art

[0002] A fluidized bed gasification furnace for gasifying solid raw materials such as biomass and coal in a low-temperature fluidized bed at 700°C or higher and 900°C or lower has been developed. The fluidized bed gasification furnace includes a gasification tank and a fluidizing gas supply unit. The gasification tank houses a fluid medium. The fluidizing gas supply unit introduces fluidizing gas from the bottom of the gasification tank. Thereby, a fluidized bed of the fluid medium is formed in the gasification tank. When solid raw materials are supplied to the gasification tank in which the fluidized bed is formed, the solid raw materials are gasified by the heat possessed by the fluidized bed (fluid medium).

[0003] Generally, silica sand is adopted as the fluid medium used in the fluidized bed gasification furnace. Therefore, when the solid raw material contains an alkali metal, silica (SiO2) contained in the silica sand reacts with the alkali metal to generate a composite oxide that melts at about 800°C. Therefore, the composite oxide melts in the gasification tank, and the fluid medium agglomerates (agglomeration) due to the melted composite oxide. Then, the fluid medium may cause poor fluidity, the fluidized bed may not be formed, or the gasification tank itself and the equipment connected to the gasification tank may be blocked by the agglomerated fluid medium.

[0004] Therefore, a technique has been developed to wash biomass with sulfuric acid water to remove alkali metals from the biomass before supplying it to the gasification tank (for example, Patent Document 1).

Prior Art Documents

[0006] However, in techniques such as the one described in Patent Document 1 above, which involves washing with sulfuric acid water, sulfuric acid and other sulfur components are supplied to the gasification tank along with the biomass. As a result, sulfur compounds such as sulfur oxides (SOx) are generated in the gasification tank. These sulfur compounds cause corrosion. Therefore, a dedicated device is required in the gasification tank or downstream equipment to remove these sulfur compounds.

[0007] In view of these issues, this disclosure aims to provide a fluidized bed apparatus that can avoid the generation of sulfur compounds and suppress the aggregation of the fluidized medium. [Means for solving the problem]

[0008] To solve the above problems, a fluidized bed apparatus according to one aspect of the present disclosure includes: a combustion furnace for heating a fluidized medium having particle sizes represented by a first particle size distribution; a cyclone for separating a solid-gas mixture supplied from the combustion furnace into solids having particle sizes greater than or equal to a separation threshold but less than the mode of the first particle size distribution, solids having particle sizes less than the separation threshold, and combustion exhaust gas; a connecting channel for connecting the cyclone and the combustion furnace; a raw material supply unit for supplying solid raw materials to the combustion furnace or the connecting channel; and a preventive agent supply unit for supplying a preventive agent containing either or both calcium and aluminum, at least a portion of which has a particle size less than the separation threshold in the combustion furnace, to the connecting channel. In the connecting channel, the inhibitor has a particle size represented by the second particle size distribution, and the mode of the second particle size distribution is between 29% and 50% of the mode of the first particle size distribution. ru.

[0010] Furthermore, the inhibitor supply unit may supply inhibitors that are 20 μm or larger and 1 mm or smaller.

[0011] Furthermore, the connecting channel may have a seal pot in which a fluidized bed of the fluidizing medium is formed, and the inhibitor supply unit may supply the inhibitor to the seal pot.

[0012] Furthermore, the connecting channel may have a gasifier, the seal pot may be provided between the gasifier and the combustion furnace, and the raw material supply unit may supply solid raw materials to the gasifier. [Effects of the Invention]

[0013] According to this disclosure, it is possible to avoid the generation of sulfur compounds and suppress the aggregation of the fluid medium. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a diagram illustrating a fluidized bed apparatus according to an embodiment. [Figure 2] Figure 2 is a diagram illustrating the first seal pot. [Figure 3] Figure 3 illustrates the relationship between the temperature of the fluid medium and the occurrence rate of complex oxides. [Figure 4] Figure 4 shows an SEM image of the flow medium when complex oxides are formed. [Figure 5] Figure 5 illustrates the particle size distribution of the fluid medium and inhibitor. [Modes for carrying out the invention]

[0015] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, specific numerical values, etc., shown in these embodiments are merely illustrative for ease of understanding and do not limit this disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

[0016] [Fluidized bed apparatus 100] Figure 1 is a diagram illustrating the fluidized bed apparatus 100 according to this embodiment. In Figure 1, solid arrows indicate the flow of solid materials such as solid raw material R, fluidizing medium F, and inhibitor A. In Figure 1, dashed arrows indicate the flow of gases such as combustion exhaust gas EX, gasification gas GG, and fluidizing gas RG.

[0017] As shown in FIG. 1, the fluidized bed apparatus 100 includes a combustion furnace 110, a first pipe 112, a cyclone 120, a connection channel 130, a heat exchanger 140, a dust removal device 142, a raw material supply unit 150, and an inhibitor supply unit 160.

[0018] In the present embodiment, the fluidized bed apparatus 100 is a circulating fluidized bed gasification system, and a fluid medium F is circulated as a heat medium through the combustion furnace 110, the first pipe 112, the cyclone 120, and the connection channel 130.

[0019] The fluid medium F has a particle size represented by a first particle size distribution. The first particle size distribution is a distribution in which the most frequent value is, for example, within the range of 400 μm or more and 700 μm or less. The fluid medium F is composed of silica sand. Note that the fluid medium F may include either or both of dolomite and kanran stone in addition to silica sand.

[0020] The combustion furnace 110 has a cylindrical shape. The first pipe 112 is connected to the upper part of the combustion furnace 110. The fifth pipe 232 of the connection channel 130 described later is connected to the lower part of the combustion furnace 110. Unburned char C and the fluid medium F from the gasification furnace 220 of the connection channel 130 described later are introduced into the combustion furnace 110 through the fifth pipe 232. The combustion furnace 110 burns unburned char C (fuel) with air to heat the fluid medium F to 900°C or more and 1000°C or less. When the amount of heat is insufficient, external fuel, hot gas, or the like is supplied to the combustion furnace 110.

[0021] The first pipe 112 connects the upper part of the combustion furnace 110 and the cyclone 120 described later. The fluid medium F and the combustion exhaust gas EX heated in the combustion furnace 110 are sent to the cyclone 120 through the first pipe 112.

[0022] The cyclone 120 includes a body 122, an inlet 124, an upper outlet 126, and a lower outlet 128. The body 122 is cylindrical in shape. At least a portion of the body 122 is conical in shape, for example, with a diameter that gradually decreases as it extends vertically downward. The inlet 124 is formed on the side of the body 122. The combustion furnace 110 is connected to the inlet 124 via a first pipe 112.

[0023] The upper outlet 126 is provided above the inlet 124 in the main body 122. In this embodiment, the upper outlet 126 is formed on the upper surface of the main body 122. The lower outlet 128 is provided below the inlet 124 in the main body 122. In this embodiment, the lower outlet 128 is formed on the bottom surface of the main body 122.

[0024] The cyclone 120 separates the solid-gas mixture supplied from the combustion furnace 110 through the inlet 124. The cyclone 120 separates the solid-gas mixture into solid particles having a particle size greater than or equal to the separation threshold, and solid particles and combustion exhaust gas EX having a particle size less than the separation threshold. The separation threshold is a value less than the mode of the first particle size distribution (400 μm or more and 700 μm or less). For example, the separation threshold is 150 μm.

[0025] As will be explained in more detail later, the solid-gas mixture includes the fluid medium F, inhibitor A, silicate S, and combustion exhaust gas EX. The solid particles with a particle size above the separation threshold include the fluid medium F, inhibitor A, and silicate S. The solid particles with a particle size below the separation threshold include silicate S.

[0026] Therefore, the combustion exhaust gas EX and silicate S separated by the cyclone 120 are sent to the heat exchanger 140 through the upper outlet 126. In other words, the silicate S, along with the combustion exhaust gas EX, is removed from the circulation path of the fluid medium F by the cyclone 120. Then, the combustion exhaust gas EX and silicate S are heat-exchanged by the heat exchanger 140. The heat exchanger 140 is, for example, a boiler. The combustion exhaust gas EX and silicate S, heat-exchanged by the heat exchanger 140, are then separated into combustion exhaust gas EX and silicate S by the dust removal device 142.

[0027] Meanwhile, the high-temperature fluid medium F, inhibitor A, and silicate S separated by the cyclone 120 are introduced into the combustion furnace 110 through the connecting channel 130. The connecting channel 130 connects the lower outlet 128 of the cyclone 120 to the lower part of the combustion furnace 110.

[0028] In this embodiment, the connecting channel 130 includes a second pipe 202, a first seal pot 210, a third pipe 212, a gasifier 220, a fourth pipe 222, a second seal pot 230, and a fifth pipe 232.

[0029] The second pipe 202 connects the lower outlet 128 of the cyclone 120 to the first seal pot 210.

[0030] The first seal pot 210 (loop seal) fluidizes the fluid medium F introduced from the cyclone 120 through the second piping 202, forming a fluidized bed.

[0031] Figure 2 is a diagram illustrating the first seal pot 210. The first seal pot 210 includes a storage tank 210a, a wind box 210b, and a blower 210c.

[0032] The containment tank 210a contains the fluid medium F introduced from the cyclone 120. An inlet 210d is formed in the ceiling of the containment tank 210a. The second pipe 202 is connected to the inlet 210d. An outlet 210e is formed on the side of the containment tank 210a. The third pipe 212 is connected to the outlet 210e. In this embodiment, the bottom surface of the containment tank 210a is composed of a dispersion plate with multiple holes formed therein.

[0033] A partition plate 210f is provided inside the containment tank 210a, extending vertically downward from the ceiling. The partition plate 210f divides the containment tank 210a into region 210g and region 210h. Region 210g is the region where the inlet 210d is formed. Region 210h is the region where the outlet 210e is formed. The tip of the partition plate 210f extends vertically downward from the lower end of the outlet 210e. The configuration with the partition plate 210f prevents the inflow of combustion exhaust gas EX from the cyclone 120 to the gasifier 220 and the inflow of gasification gas GG from the gasifier 220 to the cyclone 120.

[0034] The wind box 210b is installed below the containment tank 210a. The blower 210c introduces fluidizing gas RG into the wind box 210b. The fluidizing gas RG is, for example, either water vapor or nitrogen, or both. The fluidizing gas RG introduced into the wind box 210b is introduced into the containment tank 210a from the bottom surface (dispersion plate) of the containment tank 210a.

[0035] The discharge side of the blower 210c is connected to the wind box 210b. The blower 210c introduces the fluidizing gas RG into the wind box 210b at a flow rate that allows a fluidized bed of the fluidizing medium F to form in the containment tank 210a. Therefore, the high-temperature fluidizing medium F introduced from the cyclone 120 through the second piping 202 is fluidized by the fluidizing gas RG, and a fluidized bed (e.g., a bubbly fluidized bed) is formed in the containment tank 210a.

[0036] As further fluidizing fluid F is introduced from cyclone 120, the vertical position of the fluidized bed rises, causing the fluidizing fluid F to overflow from the lower end of outlet 210e and be introduced into gasifier 220 through third piping 212.

[0037] Returning to Figure 1, the gasifier 220 is, for example, a fluidized bed gasifier. The gasifier 220 fluidizes the high-temperature fluidized medium F introduced from the cyclone 120 with a fluidizing gas RG. The fluidizing gas RG is either water vapor or nitrogen, or both. The following example will use the case where the fluidizing gas RG is water vapor.

[0038] In this embodiment, the gasifier 220 includes a gasification tank 220a and a fluidized gas introduction section 220b. The gasification tank 220a contains a fluidized medium F and a solid raw material R. In this embodiment, the bottom surface of the gasification tank 220a is composed of a dispersion plate with a plurality of holes formed therein.

[0039] The fluidizing gas introduction section 220b introduces steam into the gasification tank 220a. The fluidizing gas introduction section 220b includes a wind box 220c and a blower 220d. The wind box 220c is located below the gasification tank 220a. The blower 220d introduces steam into the wind box 220c. The steam introduced into the wind box 220c is introduced into the gasification tank 220a from the bottom surface (dispersion plate). The discharge side of the blower 220d is connected to the wind box 220c. The blower 220d introduces steam into the wind box 220c at a flow rate that allows a fluidized bed of the fluidizing medium F to form in the gasification tank 220a. Therefore, the high-temperature fluidizing medium F introduced from the cyclone 120 is fluidized by the steam, and a fluidized bed (e.g., a bubbly fluidized bed) is formed in the gasification tank 220a.

[0040] The raw material supply unit 150 supplies solid raw material R to the gasification tank 220a. The solid raw material R is, for example, biomass. The biomass is one or more of the following: woody biomass, herbaceous biomass, and waste biomass. Woody biomass is, for example, wood chips, sawdust, tree bark, etc. Herbaceous biomass is, for example, wheat straw, rice straw, etc. Waste biomass is, for example, empty fruit bunches (EFB) and palm kernel shells (PKS) resulting from the production of palm oil from palm trees. In addition to biomass, the solid raw material R may also include coal. The coal is one or more of the following: anthracite, semi-anthracite, bituminous coal, sub-bituminous coal, and lignite.

[0041] The gasifier 220 uses the heat of the fluidized bed (fluidized medium F), which is between 700°C and 900°C, and steam to gasify (convert to steam gas) the solid raw material R supplied by the raw material supply unit 150, thereby producing gasified gas GG. The gasified gas GG produced in the gasifier 220 is introduced into a subsequent purification unit. The purification unit purifies the gasified gas GG.

[0042] The fluidized fluid medium F, which has been fluidized in the gasifier 220, is introduced into the second seal pot 230 through the fourth pipe 222. The fourth pipe 222 connects the gasifier 220a and the second seal pot 230.

[0043] The second seal pot 230 (loop seal) fluidizes the fluidized medium F introduced from the gasifier 220 through the fourth pipe 222, forming a fluidized bed. The second seal pot 230 prevents the inflow of gasification gas GG from the gasifier 220 to the combustion furnace 110 and the inflow of combustion exhaust gas EX from the combustion furnace 110 to the gasifier 220. The configuration of the second seal pot 230 is substantially the same as that of the first seal pot 210, so a detailed explanation is omitted here. The fluidized medium F that overflows from the second seal pot 230 is returned to the combustion furnace 110 through the fifth pipe 232.

[0044] Thus, in the fluidized bed apparatus 100 according to this embodiment, the fluidized medium F circulates through the combustion furnace 110, the first pipe 112, the cyclone 120, the second pipe 202, the first seal pot 210, the third pipe 212, the gasification furnace 220, the fourth pipe 222, the second seal pot 230, and the fifth pipe 232 in this order, and is then introduced back into the combustion furnace 110.

[0045] Furthermore, the combustion furnace 110 receives the residue (unburned char C) of the raw material remaining after the solid raw material R has been gasified in the gasifier 220, through the fifth pipe 232. Therefore, the unburned char C introduced from the gasifier 220 to the combustion furnace 110 is used as fuel in the combustion furnace 110.

[0046] As described above, the fluid medium F is heated to between 900°C and 1000°C in the combustion furnace 110, and a fluidized bed of the fluid medium F is formed in the gasification furnace 220 at between 700°C and 900°C. Then, the solid raw material R is introduced into the gasification furnace 220 to produce gasified gas GG.

[0047] Here, if the solid raw material R contains alkali metals (e.g., sodium, potassium), then in the combustion furnace 110 and the gasification furnace 220, the silica (SiO2) contained in the silica sand constituting the fluid medium F reacts with the alkali metals to produce complex oxides. Alkali metals are found in biomass.

[0048] Figure 3 illustrates the relationship between the temperature of the fluid medium F and the incidence of complex oxides. In Figure 3, the horizontal axis represents the temperature of the fluid medium F [°C]. In Figure 3, the vertical axis represents the incidence of complex oxides [%]. In Figure 3, squares indicate the case where the solid raw material R is lignite. In Figure 3, circles indicate the case where the solid raw material R is woody biomass. In Figure 3, triangles indicate the case where the solid raw material R is EFB. Note that Figure 3 shows the case where the fluid medium F and the solid raw material R are mixed in a 1:1 ratio.

[0049] Lignite contains, for example, about 1% by mass of potassium oxide (K2O) and about 1% by mass of sodium oxide (Na2O). As shown in Figure 3, when the solid raw material R is lignite, the occurrence rate of complex oxides is 0% in the range of 600°C to 700°C. Furthermore, in the range of over 700°C and up to 1100°C, the occurrence rate of complex oxides gradually increases. The occurrence rate of complex oxides at 800°C is about 15%. The occurrence rate of complex oxides at 900°C is about 50%. The occurrence rate of complex oxides at 1000°C is about 75%. The occurrence rate of complex oxides at 1100°C is about 80%. In the range of over 1100°C and up to 1200°C, the occurrence rate of complex oxides is maintained at about 80%.

[0050] Therefore, when lignite is gasified in the gasifier 220, the generation rate of complex oxides can be suppressed to a range of 0% to 50% within the temperature range of the gasifier 220, which is 700°C to 900°C.

[0051] On the other hand, woody biomass contains, for example, about 15% by mass of potassium oxide and about 5% by mass of sodium oxide. As shown in Figure 3, when the solid raw material R is woody biomass, the rate of complex oxide formation gradually increases in the range of 600°C to 1000°C. The rate of complex oxide formation at 600°C is 0%. The rate of complex oxide formation at 700°C is about 15%. The rate of complex oxide formation at 800°C is about 30%. The rate of complex oxide formation at 900°C is about 50%. The rate of complex oxide formation at 1000°C is about 60%. In the range of over 1000°C and up to 1200°C, the rate of complex oxide formation is maintained at about 60%.

[0052] Therefore, when woody biomass is gasified in the gasifier 220, the generation rate of complex oxides becomes 15% to 50% within the temperature range of the gasifier 220, which is 700°C to 900°C.

[0053] Furthermore, EFB contains, for example, about 20% by mass of potassium oxide and about 1% by mass of sodium oxide. As shown in Figure 3, when the solid raw material R is EFB, the occurrence rate of complex oxides gradually increases in the range of 600°C to 1000°C. The occurrence rate of complex oxides is about 10% at 600°C. The occurrence rate of complex oxides is about 25% at 700°C. The occurrence rate of complex oxides is about 40% at 800°C. The occurrence rate of complex oxides is about 60% at 900°C. The occurrence rate of complex oxides is about 80% at 1000°C. In the range of over 1000°C and up to 1200°C, the occurrence rate of complex oxides is maintained at about 80%.

[0054] Therefore, when EFB is gasified in the gasifier 220, the generation rate of complex oxides becomes 25% to 60% within the temperature range of the gasifier 220, which is 700°C to 900°C.

[0055] Thus, when biomass such as woody biomass and EFB is gasified in the gasifier 220, unlike lignite, complex oxides are generated in the range of 700°C to 800°C. In other words, when gasifying biomass, complex oxides are generated at a lower temperature than when gasifying lignite.

[0056] The composite oxide melts at around 700°C. Therefore, in the gasification furnace 220, the fluid medium F is coated with the molten composite oxide.

[0057] Figure 4 shows a scanning electron microscope (SEM) image of the fluid medium F when the complex oxide is formed. As shown in Figure 4, it can be confirmed that the fluid medium F is coated with the complex oxide.

[0058] Therefore, in the gasifier 220, combustion furnace 110, etc., the fluid medium F aggregates with other fluid medium F due to the complex oxides adhering to the surface of the fluid medium F. When the fluid medium F aggregates, it causes poor fluidity, which may prevent the formation of a fluidized bed in the first seal pot 210, gasifier 220, and second seal pot 230, or cause blockage of the second piping 202, first seal pot 210, third piping 212, gasifier 220, fourth piping 222, second seal pot 230, and fifth piping 232 with the aggregated fluid medium F.

[0059] Therefore, the fluidized bed apparatus 100 according to this embodiment includes a inhibitor supply unit 160. Returning to Figure 1, the inhibitor supply unit 160 supplies inhibitor A to the second seal pot 230. In this embodiment, the inhibitor supply unit 160 supplies inhibitor A to the region of the second seal pot 230 that includes the inlet to which the fourth pipe 222 is connected. The inhibitor supply unit 160 is composed of, for example, a screw feeder or a hydrogen purging mechanism.

[0060] Furthermore, the inhibitor supply unit 160 supplies inhibitor A in an amount that is 5 to 10 times the weight of alkali metals contained in the solid raw material R supplied by the raw material supply unit 150. The alkali metal content in the solid raw material R is measured in advance.

[0061] Inhibitor A contains either or both calcium and aluminum. Inhibitor A is a mineral such as limestone, slaked lime, dolomite, olivine, or bauxite. By using a mineral as inhibitor A, the cost required for inhibitor A can be reduced.

[0062] Inhibitor A reacts with alkali metals and silica sand. As a result, silicate S is produced. For example, if inhibitor A contains calcium, the reaction shown in formula (1) below proceeds. Then, calcium potassium silicate (K 1-n Ca nSiO) is produced. Also, if inhibitor A contains aluminum, the reaction shown in formula (2) below proceeds. Then, potassium aluminum silicate (K 1-2n / 3 Al 2n / 3 SiO₂ is generated. 4K+CaO+3SiO2+O2→ K4CaSi3O9…Equation (1) 2K+Al2O3+4SiO2+1 / 2O2→ K2Al2Si4O 12 …Formula (2)

[0063] Therefore, the formation of complex oxides can be suppressed by the inhibitor A incorporating alkali metals contained in the ash generated from the solid raw material R, thereby producing silicate S. Furthermore, the formation of complex oxides can be reduced by the inhibitor A incorporating alkali metals contained in the complex oxide, thereby producing silicate S.

[0064] The melting points of silicates S, such as calcium potassium silicate and aluminum potassium silicate, are higher than the melting point of potassium silicate (below 1100°C). For example, the melting point of silicate S is 1400°C or higher. Therefore, by supplying the inhibitor A from the inhibitor supply unit 160, it is possible to suppress the formation of complex oxides and reduce the amount of complex oxides, thereby suppressing the aggregation of the fluid medium F.

[0065] Furthermore, the inhibitor supply unit 160 supplies inhibitor A to the second seal pot 230 where the fluidized bed of the fluidized medium F is formed. In other words, inhibitor A is supplied to the fluidized bed of the fluidized medium F. Therefore, it becomes possible to efficiently mix inhibitor A and the fluidized medium F. This increases the frequency of contact between the alkali metals contained in the composite oxides and ash generated from the solid raw material R that adhere to the surface of the fluidized medium F and inhibitor A, making it possible to efficiently convert the alkali metals into silicates S.

[0066] Furthermore, the inhibitor A is mixed with the fluid medium F in the second seal pot 230. As a result, the inhibitor A collides with the fluid medium F. Consequently, at least a portion of the inhibitor A is crushed and its particle size is reduced. Therefore, the inhibitor supply unit 160 supplies inhibitor A with a particle size below the separation threshold in the combustion furnace 110, at least a portion of which is present.

[0067] This allows at least a portion of the silicate S, which is produced by the reaction of the crushed and reduced-particle-size inhibitor A, to be separated from the fluid medium F by the cyclone 120. Therefore, the silicate S can be carried along with the combustion exhaust gas EX and discharged to the outside from the upper outlet 126. In other words, the alkali metals contained in the solid raw material R are converted into silicate by the inhibitor A, and then discharged to the outside from the circulation path of the fluid medium F by the cyclone 120.

[0068] Specifically, in the second seal pot 230 (connecting channel 130), the inhibitor A has a particle size represented by the second particle size distribution. Figure 5 illustrates the particle size distribution of the fluid medium F and inhibitor A. In Figure 5, the horizontal axis represents particle size [μm]. In Figure 5, the vertical axis represents volume-based frequency [%]. Also, in Figure 5, the dashed and dotted lines represent the particle size distribution of the fluid medium F, i.e., the first particle size distribution. In Figure 5, the solid line represents the particle size distribution of inhibitor A, i.e., the second particle size distribution.

[0069] As shown in Figure 5, the first particle size distribution is one in which the most frequent value is within the range of 400 μm to 700 μm. For example, the most frequent value of the first particle size distribution shown by the dashed line is approximately 430 μm. The most frequent value of the first particle size distribution shown by the dashed line is approximately 650 μm. The most frequent value of the second particle size distribution shown by the solid line is approximately 190 μm. In other words, the most frequent value of the second particle size distribution is between 29% and 50% of the most frequent value of the first particle size distribution.

[0070] Therefore, in cyclone 120, silicate S (inhibitor A) and the fluid medium F can be efficiently separated.

[0071] Furthermore, to improve reactivity with alkali metals, a larger specific surface area of ​​inhibitor A is preferable. In other words, a smaller particle size of inhibitor A is preferable. However, if the particle size of inhibitor A is too small, it will scatter in the second seal pot 230 and will not mix with the fluid medium F.

[0072] Therefore, the inhibitor supply unit 160 supplies inhibitor A that is 20 μm or larger. This prevents the inhibitor A from scattering in the second seal pot 230 and makes it possible to mix inhibitor A with the fluid medium F. This increases the frequency of contact between the alkali metals contained in the composite oxides and ash generated from the solid raw material R that adhere to the surface of the fluid medium F and inhibitor A, making it possible to efficiently convert the alkali metals into silicate S.

[0073] Furthermore, if the particle size of inhibitor A is too large, it will not be fluidized in the second seal pot 230. Therefore, the inhibitor supply unit 160 supplies inhibitor A with a particle size of 1000 μm or less. This allows inhibitor A to be fluidized in the second seal pot 230. Consequently, inhibitor A having a particle size above the separation threshold can be circulated to the second seal pot 230, the fifth pipe 232, the combustion furnace 110, the first pipe 112, the cyclone 120, the second pipe 202, the first seal pot 210, the third pipe 212, and the gasification furnace 220. As a result, during the circulation process, the fluid medium F and ash can be brought into contact with inhibitor A, making it possible to efficiently convert alkali metals into silicates S.

[0074] Furthermore, even if the inhibitor A is above the separation threshold, it is crushed and its particle size is reduced upon collision with the fluid medium F. Therefore, ultimately, inhibitor A is separated by cyclone 120 and discarded externally along with the combustion exhaust gas EX.

[0075] As described above, the fluidized bed apparatus 100 according to this embodiment is equipped with an inhibitor supply unit 160. This makes it possible for the fluidized bed apparatus 100 to avoid the generation of sulfur compounds and suppress the aggregation of the fluidized medium F.

[0076] While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of this disclosure.

[0077] For example, in the embodiment described above, the inhibitor supply unit 160 is shown as supplying inhibitor A to the region of the second seal pot 230 that includes the inlet to which the fourth pipe 222 is connected. This makes it possible to increase the residence time of inhibitor A in the second seal pot 230, and to increase the contact time between the distribution and fluid medium F and inhibitor A. However, the inhibitor supply unit 160 may also supply inhibitor A to the region of the second seal pot 230 that includes the outlet to which the fifth pipe 232 is connected. In this case, the inhibitor supply unit 160 can omit a material seal such as a screw feeder or a hydrogen purging mechanism.

[0078] Furthermore, in the above embodiment, the case in which the inhibitor supply unit 160 supplies inhibitor A to the second seal pot 230 was given as an example. However, the inhibitor supply unit 160 may supply inhibitor A to either or both of the first seal pot 210 and the gasification furnace 220. Even in this case, inhibitor A can be supplied to the fluidized bed of the fluidized medium F. Therefore, it becomes possible to efficiently mix inhibitor A and the fluidized medium F. This increases the frequency of contact between the alkali metals contained in the composite oxides and ash generated from the solid raw material R attached to the surface of the fluidized medium F and inhibitor A, making it possible to efficiently convert alkali metals into silicates S.

[0079] Furthermore, in the above embodiment, an example was given in which the connecting channel 130 is equipped with a gasifier 220. However, the gasifier 220 is not an essential component. If the fluidized bed apparatus is not equipped with a gasifier 220, the inhibitor supply unit 160 supplies inhibitor A to the connecting channel 130. This makes it possible to avoid the generation of sulfur compounds and suppress the aggregation of the fluidized medium F.

[0080] Furthermore, in the above embodiment, the case in which inhibitor A is a mineral was given as an example. However, inhibitor A does not have to be a mineral, as long as it contains at least one or both of calcium and aluminum.

[0081] This disclosure can contribute, for example, to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy," Goal 13, "Take urgent action to combat climate change and its impacts," and Goal 15, "Promote sustainable forest management, combat desertification, halt and reverse land degradation and halt biodiversity loss." [Explanation of Symbols]

[0082] 100 Fluidized Bed System 110 Combustion furnace 120 Cyclone 124 Entrance 126 Upper exit 128 Lower Exit 130 Connection channel 150 Raw material supply department 160 Inhibitor supply unit 210 First Seal Pot (Seal Pot) 220 Gasification Furnaces 230 Second Seal Pot (Seal Pot)

Claims

1. A combustion furnace for heating a fluid medium having particle sizes represented by a first particle size distribution, A cyclone that separates the solid-gas mixture supplied from the combustion furnace into solid matter having a particle size greater than or equal to a separation threshold less than the mode of the first particle size distribution, and solid matter having a particle size less than the separation threshold and combustion exhaust gas. A connecting channel connecting the cyclone and the combustion furnace, A raw material supply unit that supplies solid raw materials to the combustion furnace or the connecting channel, A preventive agent supply unit supplies a preventive agent containing either or both calcium and aluminum, at least a portion of which has a particle size below the separation threshold in the combustion furnace, to the connecting channel, Equipped with, In the aforementioned connecting channel, the inhibitor has a particle size represented by the second particle size distribution, A fluidized bed apparatus in which the mode of the second particle size distribution is 29% or more and 50% or less of the mode of the first particle size distribution.

2. The fluidized bed apparatus according to claim 1, wherein the inhibitor supply unit supplies the inhibitor with a thickness of 20 μm or more and a thickness of 1 mm or less.

3. The connecting channel has a seal pot in which the fluidized bed of the fluidized medium is formed. The fluidized bed apparatus according to claim 1 or 2, wherein the inhibitor supply unit supplies the inhibitor to the seal pot.

4. The aforementioned connecting channel has a gasification furnace, The seal pot is provided between the gasification furnace and the combustion furnace, The fluidized bed apparatus according to claim 3, wherein the raw material supply unit supplies the solid raw material to the gasification furnace.

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