Biomass carbonization equipment

Abstract

To provide a technology for efficiently operating a biomass carbonization plant while suppressing blockage caused by tar buildup. [Solution] One aspect of this disclosure provides a biomass carbonization apparatus comprising: a carbonization furnace for carbonizing biomass; a combustion furnace for burning the gas discharged from the carbonization furnace; a duct connecting the carbonization furnace and the combustion furnace; and an oxygen-containing gas supply unit for supplying oxygen-containing gas to the duct during operation of the carbonization furnace.

Description

Technical Field

[0001] The present disclosure relates to a biomass carbonization device.

Background Art

[0002] In equipment for carbonizing raw materials, various countermeasures have been studied because by-products generated in the carbonization process may affect the equipment. For example, Patent Document 1 discloses a configuration in which air is introduced into the carbonization chamber of a coke oven to burn and remove the carbon on the furnace wall. Further, Patent Documents 2 and 3 disclose configurations in which deposits are burned by supplying air to the carbonization furnace and the duct during the stoppage of the waste carbonization furnace.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In equipment for carbonizing biomass, tar is generated as a by-product by the carbonization of biomass, and thus tar may cause blockage of the equipment. However, for example, the method described in Patent Document 1 is a method for removing deposits generated in the carbonization chamber where dry distillation of raw materials is performed, and does not assume that by-products flow out of the carbonization chamber. On the other hand, if the methods described in Patent Documents 2 and 3 are to be implemented, it is necessary to stop the carbonization furnace, which may reduce the operation efficiency.

[0005] This disclosure is made in view of the above, and aims to provide a technology for efficiently operating a biomass carbonization plant while suppressing blockage of the equipment due to tar buildup. [Means for solving the problem]

[0006] To achieve the above objective, a biomass carbonization apparatus according to one embodiment of the present disclosure includes a carbonization furnace for carbonizing biomass, a combustion furnace for burning the gas discharged from the carbonization furnace, a duct connecting the carbonization furnace and the combustion furnace, and an oxygen-containing gas supply unit for supplying oxygen-containing gas to the duct during operation of the carbonization furnace.

[0007] According to the biomass carbonization apparatus described above, by supplying oxygen-containing gas to the duct, the tar generated in the carbonization furnace can be burned in the duct, thus preventing blockage of the equipment due to tar adhering to the duct. In addition, by supplying oxygen-containing gas during the operation of the carbonization furnace, the amount of equipment shutdown required for cleaning and other purposes can be reduced, and biomass carbonization by the biomass carbonization apparatus can be performed more efficiently.

[0008] The oxygen concentration in the gas inside the duct after the supply of the oxygen-containing gas may be 10 vol% or less. In a biomass carbonization apparatus, the gas discharged from the carbonization furnace may contain dust and other particles, which could lead to an explosion. In contrast, by setting the oxygen concentration inside the duct to 10 vol% or less, the possibility of an explosion inside the duct can be reduced while burning the tar.

[0009] The carbonization temperature in the carbonization furnace may be set to 300°C or lower. When the carbonization temperature is 300°C or lower, the amount of tar in the gas discharged from the carbonization furnace is low, which increases the oxygen concentration in the duct and can increase the likelihood of explosion. Therefore, when the carbonization temperature is 300°C or lower, the effect of avoiding explosion is more pronounced by setting the oxygen concentration in the duct to 10 vol% or lower. [Effects of the Invention]

[0010] According to this disclosure, a technology is provided for efficiently operating a biomass carbonization plant while suppressing blockage of the equipment due to tar buildup. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a flowchart illustrating the outline of a method for producing a biomass solid fuel in one form. [Figure 2] Figure 2 is a schematic diagram of a biomass carbonization apparatus according to one configuration. [Modes for carrying out the invention]

[0012] The embodiments for implementing this disclosure will be described in detail below with reference to the attached drawings. In the description of the drawings, the same elements will be denoted by the same reference numeral, and redundant explanations will be omitted.

[0013] [Method for producing biomass solid fuel] Figure 1 is a flowchart illustrating the outline of a method for producing biomass solid fuel using a biomass carbonization apparatus, including a biomass carbonization apparatus according to one embodiment of the present disclosure. As shown in Figure 1, the biomass that will be used as the raw material for biomass solid fuel is transformed into pelletized biomass molded bodies (White Pellet: hereinafter referred to as "WP") through a crushing process (S01) and a molding process (S02). This WP is carbonized by heating in a heating process (S03) to become biomass solid fuel (Pelletizing Before Torrefaction: hereinafter referred to as "PBT"). This PBT is then transformed into a product through a classification and cooling process (S04) as needed.

[0014] The crushing step (S01) is a step in which the raw material biomass (raw material biomass) is crushed and then crushed. The type of raw material biomass is not particularly limited and can be selected from woody and herbaceous plants. The tree species and part of the raw material biomass are not particularly limited, but for example, in one embodiment, the raw material may include at least one selected from the group consisting of rubber tree, acacia, Dipterocarpaceae tree species, radiata pine, and a mixture of larch, spruce, and birch. Larch, spruce, and birch may each be used individually as raw material biomass, but two or more, preferably three, of these can be used as a mixture. In addition, the raw material may include at least one (or a mixture of two or three) selected from the group consisting of a mixture of spruce, pine, and fir.

[0015] Furthermore, the raw materials may also include other tree species not mentioned above. In one embodiment of this disclosure, the content of one or more species selected from the group consisting of rubber tree, acacia, Dipterocarpaceae tree species, radiata pine, and a mixture of larch, spruce, and birch is preferably 50% by weight or more, more preferably 80% by weight or more, and may be 100% by weight.

[0016] Furthermore, Douglas fir, Western hemlock, Japanese cedar, cypress, Scots pine, old almond wood, almond shells, walnut shells, sago palm, EFB (empty fruit clusters from palm oil processing residue), meranti, acacia wood, acacia bark, eucalyptus, teak, spruce + birch, rubber, etc. may also be used as raw materials.

[0017] The particle size of the biomass after grinding is not particularly limited, but can be approximately 100 μm to 3000 μm on average, preferably 400 μm to 1000 μm on average. A known method for measuring the particle size of the biomass powder may be used.

[0018] The forming process (S02) is a process of forming the crushed biomass into a块状 form using a known forming technique. The biomass formed body (WP), which is a块状 biomass after forming, can be made into pellets or briquettes. The size of WP can be appropriately changed. In the forming process, no binder such as a binder is added, and it is formed by compressing and pressurizing the crushed biomass.

[0019] The heating process (S03) is a process of heating the biomass formed body (WP) at 150°C to 400°C (low-temperature carbonization) to obtain a biomass solid fuel (PBT) having strength and water resistance while maintaining the shape as a formed body. The heating process is performed using the biomass carbonization device 100 described later.

[0020] The heating temperature (also referred to as the carbonization temperature, which is the heating temperature of PBT in the kiln body 20 of the rotary kiln 2 described later) is appropriately determined according to the biomass and the shape and size of the块状 material, but is set to 300°C or lower. As the heating temperature when manufacturing PBT from the biomass formed body (WP), it is preferably 200°C or higher and 300°C or lower, more preferably 230°C or higher and lower than 300°C. Further, it is preferably 230°C to 280°C. The heating time in the heating process is not particularly limited, but can be 0.2 hours to 3 hours.

[0021] The classification and cooling process (S04) is a process of performing classification and cooling in order to commercialize the PBT obtained by the heating process. Classification and cooling may be omitted, or only one of the processes may be performed. If necessary, the classified and cooled PBT becomes a solid fuel product.

[0022] The biomass solid fuel obtained after the heating process (S03) preferably has a COD (Chemical Oxygen Demand) of immersion water of 3000 ppm or less. Here, the COD (Chemical Oxygen Demand) of immersion water when biomass solid fuel is immersed in water (also simply referred to as "COD") refers to the COD value obtained by preparing the immersion water sample for COD measurement in accordance with the method described in Section 1, Preparation of Test Solution: Sample Solution (a) of the Environmental Agency Notification No. 13 of 1973, "Method for Testing Metals, etc. Contained in Industrial Waste," and analyzing it according to JIS K0102(2019)-17.

[0023] Furthermore, the biomass solid fuel obtained after the heating process preferably has a pulverability index (HGI) of 15 to 60, and more preferably 20 to 60, based on JIS M 8801 (2008). The biomass solid fuel also has a BET specific surface area of ​​0.15 m². 2 / g~0.8m 2 It is preferable that it be / g, and 0.15m 2 / g~0.7m 2 It is more preferable that the amount is / g. Furthermore, the biomass solid fuel is preferably at an equilibrium moisture content of 15wt% to 65wt% after immersion in water, and more preferably at 15wt% to 60wt%.

[0024] Furthermore, the biomass solid fuel obtained after the heating process has a fuel ratio (fixed carbon / volatile matter) of 0.2 to 0.8, an anhydrous base higher heating value of 4800 kcal / kg to 7000 kcal / kg, an oxygen-to-carbon molar ratio (O / C) of 0.1 to 0.7, and a hydrogen-to-carbon molar ratio (H / C) of 0.8 to 1.3. By having the physical properties of the biomass solid fuel after the heating process within this range, it is possible to reduce COD in wastewater during storage, reduce pulverization, and improve handling during storage. The physical properties of the biomass solid fuel can be adjusted to the above range by, for example, adjusting the tree species and part of the biomass used as raw material, the heating temperature in the heating process, etc. The industrial analysis values, elemental analysis values, and higher heating values ​​in this specification are based on JIS M 8812 (2006), JIS M 8813 (2006), and JIS M 8814 (2003), respectively.

[0025] Furthermore, the biomass solid fuel obtained after the heating process will reach a maximum temperature of less than 200°C in the self-heating test. The self-heating test is a test specified in "United Nations: Recommendations on the Transport of Dangerous Goods: Manual of Test Methods and Criteria: 5th Edition: Self-heating Test".

[0026] [Biomass carbonization equipment] Next, the biomass carbonization apparatus 100 used in the heating process (S03) will be explained with reference to Figure 2. Figure 2 is a schematic diagram illustrating the biomass carbonization apparatus used in the heating process.

[0027] As shown in Figure 2, the biomass carbonization apparatus 100 includes a hopper 1, a rotary kiln 2 (carbonization furnace), a cooler 3, and a gas treatment facility 4. The hopper 1 and the rotary kiln 2 are controlled by a control unit (not shown).

[0028] Hopper 1 has the function of storing biomass molded bodies (WP). The WP stored in hopper 1 is sequentially supplied to rotary kiln 2 and heated in rotary kiln 2. By heating the WP, biomass solid fuel (PBT) is produced. After the PBT produced in rotary kiln 2 is discharged from rotary kiln 2, it is cooled by cooler 3.

[0029] Rotary kiln 2 is a so-called externally heated type. Rotary kiln 2 has a kiln body 20 into which the material to be heated, WP, is introduced and heated (low-temperature carbonization), and a heating unit 30 that heats the kiln body 20.

[0030] The kiln body 20 is roughly cylindrical in shape. Biomass molded material (WP), which is the material to be heated, is introduced into the kiln from one end, and the biomass solid fuel (PBT) after heating (low-temperature carbonization) is discharged from the other end. Therefore, an inlet 21 for introducing the biomass molded material is provided at one end of the kiln body 20. The other end of the kiln body 20 is provided with a PBT outlet 22 for discharging the biomass solid fuel (PBT) that has been carbonized by heating inside the kiln body 20, and a gas outlet 23 for discharging the pyrolysis gas generated inside the kiln body 20. The PBT outlet 22 may be located below the kiln body 20, and the gas outlet 23 may be located above the kiln body 20.

[0031] The kiln body 20 is supported by the upstream roller 25 and the downstream roller 26 so as to be rotatable about an axis extending in the direction of movement of the WP. In other words, the central axis of the kiln body 20 becomes the axis of rotation of the kiln body 20.

[0032] The kiln body 20 is installed at an angle such that the upstream side (inlet 21 side) is upward and the downstream side (PBT discharge port 22 side) is downward. The installation angle of the kiln body 20 can be changed as appropriate depending on the size of the kiln body 20, the speed at which the WP moves inside the kiln body 20, etc.

[0033] The heating section 30 has a hot gas path 33 including a gas inlet 31 and a gas outlet 32. The hot gas path 33 is provided around the kiln body 20. Hot gas is supplied from the gas inlet 31 located on the outer circumference of the kiln body 20, passes through the hot gas path 33, and is discharged from the gas outlet 32. The hot gas flowing through this hot gas path 33 heats the kiln body 20 in the rotary kiln 2. Furthermore, the temperature of the kiln body 20 of the rotary kiln 2 can be controlled by appropriately changing the temperature of the hot gas supplied to the hot gas path 33. The hot gas supplied to the hot gas path 33 is gas burned in a combustion furnace, which will be described later.

[0034] The hot gas discharged from the gas outlet 32 ​​may be released into the atmosphere via the induced draft fan 37 after dust has been collected by the cyclone 35.

[0035] In Figure 2, the rotary kiln 2 is a counter-flow type where the direction of movement of the material to be heated (WP) (from the inlet 21 to the PBT outlet 22) and the direction of movement of the hot gas are opposite, but it may also be a parallel flow type. Furthermore, the oxygen concentration inside the rotary kiln 2 may be set to 10% or less.

[0036] The cooler 3 has the function of cooling the biomass solid fuel (PBT) discharged from the rotary kiln 2 to approximately room temperature. As for the cooler 3, for example, since the biomass solid fuel (PBT) is water-resistant, a method of cooling by directly spraying water onto the biomass solid fuel (PBT) may be used.

[0037] The pyrolysis gas discharged from the gas outlet 23 of the kiln body 20 is introduced into the gas treatment equipment 4. The gas treatment equipment 4 consists of a combustion furnace 41 and a duct 42.

[0038] The combustion furnace 41 burns the pyrolysis gas generated in the kiln body 20. A duct 42 is installed between the gas outlet 23 of the kiln body 20 and the combustion furnace 41, introducing the pyrolysis gas discharged from the gas outlet 23 into the combustion furnace 41. Oxygen-containing gas supplied from a gas supply source 43 is supplied to the duct 42 via a path L1. Path L1 is composed of, for example, piping. The gas supply source 43 and the path L1 supplying oxygen-containing gas from the gas supply source 43 to the duct 42 function as an oxygen-containing gas supply unit 45. This will be described later.

[0039] The combustion furnace 41 receives pyrolysis gas supplied from the kiln body 20 via a duct 42, and air supplied from the outside via an air fan 44. As a result, the pyrolysis gas is burned at a high temperature in the combustion furnace 41. The pyrolysis gas is completely combusted. The high-temperature exhaust gas generated by the combustion is introduced into the hot gas path 33 from the gas inlet 31 of the heating section 30 via piping. In this way, the exhaust gas generated by the combustion in the combustion furnace 41 can be used as hot gas to heat the kiln body 20 in the rotary kiln 2.

[0040] The pyrolysis gas to be treated in the gas treatment facility 4 described above contains tar produced by the carbonization of biomass molded bodies (WP) in the kiln body 20. When the pyrolysis gas is discharged from the kiln body 20, the tar is in gaseous form, but it may change into a liquid state due to the decrease in temperature as it moves through the duct 42. Therefore, when the pyrolysis gas is supplied to the combustion furnace 41 via the duct 42, tar may accumulate in the duct 42. Furthermore, an increase in the amount of tar accumulated in the duct 42 could potentially cause blockage of the equipment.

[0041] In contrast, the gas treatment equipment 4 described above supplies oxygen-containing gas to the duct 42 via the oxygen-containing gas supply unit 45, thereby creating an environment in the duct 42 that facilitates the combustion of tar.

[0042] Oxygen-containing gas supplied from the gas supply source 43 via path L1 is supplied into the duct 42, causing the tar to burn inside the duct 42. Burning the tar decomposes it, preventing it from accumulating inside the duct 42.

[0043] The oxygen concentration in the gas inside duct 42 after supplying oxygen-containing gas to duct 42 may be 10 vol% or less. The oxygen concentration in the gas inside duct 42 may be greater than 10 vol% as long as tar combustion is possible. However, depending on the combustible materials contained in the pyrolysis gas supplied to duct 42, supplying oxygen-containing gas to duct 42 may cause an explosion inside duct 42. In particular, as in this embodiment, the pyrolysis gas produced by the carbonization of biomass molded bodies (WP) may contain dust. Therefore, there is a possibility of a dust explosion occurring inside duct 42. In contrast, by setting the oxygen concentration in the gas inside duct 42 to 10 vol% or less, the occurrence of an explosion inside duct 42, especially a dust explosion, can be suppressed. Furthermore, an oxygen concentration of 2 vol% or more in the gas inside duct 42 makes it easier to burn tar inside duct 42. Other components of the oxygen-containing gas include, for example, inert gases such as nitrogen (N2) and argon (Ar).

[0044] Furthermore, the supply of oxygen-containing gas to duct 42 is performed while rotary kiln 2 is operating. While the biomass molded body (WP) is being heated and carbonized in rotary kiln 2, pyrolysis gas containing tar can be supplied into duct 42 from gas outlet 23. Therefore, by supplying oxygen-containing gas while rotary kiln 2 is operating, the tar supplied into duct 42 can be burned before it accumulates and adheres to the inside of duct 42. Note that the oxygen-containing gas may be supplied continuously (for example, at all times) or intermittently during the operation of rotary kiln 2. If oxygen-containing gas is supplied at all times, the combustion of tar in duct 42 can be achieved with a simpler configuration.

[0045] Furthermore, the amount of oxygen-containing gas supplied to duct 42 is not particularly limited as long as the tar can be burned within duct 42. The amount of oxygen-containing gas supplied can also be adjusted depending on whether the oxygen-containing gas is supplied to duct 42 continuously or intermittently. In addition, the amount of oxygen-containing gas suitable for tar combustion can be changed depending on the characteristics of the pyrolysis gas supplied from rotary kiln 2. In other words, how the oxygen-containing gas is supplied (supply timing, supply amount, etc.) can be appropriately changed according to the operating conditions of rotary kiln 2. Note that in this embodiment, "burning of tar within duct 42" does not mean that the tar is to be completely burned within duct 42; it is sufficient to burn the tar to the extent that it does not adhere to the walls inside duct 42.

[0046] Furthermore, the location where the oxygen-containing gas supply path L1 to the duct 42 connects to the duct 42, that is, the location where the oxygen-containing gas is introduced into the duct 42, is not particularly limited and can be provided at a suitable location between the end of the duct 42 on the gas outlet 23 side and the end on the combustion furnace 41 side. In addition, the oxygen-containing gas supply path L1 may be connected to the duct 42 at multiple locations (for example, multiple locations along the direction of movement of the pyrolysis gas). When oxygen-containing gas is supplied to the duct 42 from multiple locations, the amount of oxygen-containing gas supplied may differ from one another depending on the supply location.

[0047] [Effect] According to the biomass carbonization apparatus 100 described above, oxygen-containing gas is supplied to the duct 42 by the oxygen-containing gas supply unit (gas supply source 43 and path L1). This allows the tar generated in the rotary kiln 2, which acts as the carbonization furnace, to be burned in the duct 42, thereby preventing blockage of the equipment due to tar adhering to the duct 42. Furthermore, by supplying oxygen-containing gas into the furnace during the operation of the rotary kiln 2, which acts as the carbonization furnace, the number of times the equipment needs to be stopped for cleaning or other purposes can be reduced, and biomass carbonization by the biomass carbonization apparatus 100 can be performed more efficiently.

[0048] Conventionally, a configuration has been known in which the pyrolysis gas generated by the carbonization of biomass molded bodies (WP) in the rotary kiln 2 is burned in the combustion furnace 41, and the exhaust gas from the combustion furnace 41 is used as a heat source for heating the rotary kiln 2. In such a configuration, there is a problem that tar tends to accumulate in the duct 42 installed between the kiln body 20 of the rotary kiln 2 and the combustion furnace 41. If tar accumulation progresses in the duct 42, it may cause blockage of the equipment. Furthermore, while it is conceivable that the tar adhering to the duct 42 can be removed by cleaning, this requires stopping the operation of the equipment, which poses a challenge in terms of equipment operation efficiency. In contrast, by adopting a configuration that allows tar to be burned while the rotary kiln 2 is in operation, as described above, the number of times cleaning work requiring the equipment to be stopped can be reduced, thus enabling more efficient biomass carbonization work using the biomass carbonization device 100.

[0049] Furthermore, the oxygen concentration in the gas inside the duct 42 after the supply of oxygen-containing gas may be 10 vol% or less. In the biomass carbonization apparatus 100 described above, the gas discharged from the rotary kiln 2, which acts as a carbonization furnace, may contain dust and other particles, in which case there is a possibility of explosion. In contrast, by setting the oxygen concentration in the gas inside the duct 42 after the supply of oxygen-containing gas to 10 vol% or less, the possibility of explosion inside the duct 42 can be reduced while burning tar inside the duct 42.

[0050] Furthermore, the carbonization temperature in the rotary kiln 2 (kiln body 20) as a carbonization furnace may be set to 300°C or lower. When the carbonization temperature is 300°C or lower, the tar in the gas discharged from the carbonization furnace contains a large amount of residual volatile components derived from biomass. Therefore, the possibility of explosion when the tar is burned in the duct 42 may increase. Accordingly, when the carbonization temperature is 300°C or lower, the effect of avoiding explosions is more pronounced by setting the oxygen concentration in the gas inside the duct 42 after the supply of oxygen-containing gas to 10 vol% or lower.

[0051] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications can be made.

[0052] For example, the configuration and arrangement of each part of the biomass carbonization apparatus 100, including the rotary kiln 2, can be changed as appropriate. For example, the shape and arrangement of the biomass molded body inlet and the biomass solid fuel outlet can also be changed as appropriate. Furthermore, the biomass carbonization apparatus 100 only needs to be a device that carbonizes biomass, and the carbonized biomass may be used for purposes other than biomass solid fuel. [Explanation of Symbols]

[0053] 1...Hopper, 2...Rotary kiln, 3...Cooler, 4...Gas processing equipment, 20...Kiln body, 21...Inlet, 22...PBT outlet, 23...Gas outlet, 30...Heating section, 31...Gas inlet, 32...Gas outlet, 33...Hot gas path, 35...Cyclone, 37...Induced draft fan, 41...Combustion furnace, 42...Duct, 43...Gas supply source, 44...Air fan, 45...Oxygen-containing gas supply section, 100...Biomass carbonization equipment, L1...Path (Oxygen-containing gas supply path).

Claims

1. A carbonization furnace for carbonizing biomass, A combustion furnace for burning the gas discharged from the carbonization furnace, A duct connecting the carbonization furnace and the combustion furnace, During operation of the carbonization furnace, an oxygen-containing gas supply unit supplies oxygen-containing gas to the duct, A biomass carbonization device having the following features.

2. The biomass carbonization apparatus according to claim 1, wherein the oxygen concentration in the gas inside the duct after the supply of the oxygen-containing gas is 10 vol% or less.

3. The biomass carbonization apparatus according to claim 1 or 2, wherein the carbonization temperature in the carbonization furnace is 300°C or lower.

Images