Combustion furnace system and method for burning biomass fuel

Abstract

The present invention comprises: a combustion device 2 that uses biomass fuel T as fuel; a drying unit 32 that dries the biomass fuel T; and a supply device 7 that supplies, to the drying unit 32, heat medium gas containing at least one of exhaust gas from the combustion device 2 and gas heated by heat exchange with the exhaust gas. The supply device 7 controls at least one of a flow rate and a temperature of the heat medium gas supplied to the drying unit 32 on the basis of the moisture content of the biomass fuel T.

Description

Title of Invention: COMBUSTION FURNACE SYSTEM AND METHOD FOR BURNING BIOMASS FUEL Technical Field

[0001] The present invention relates to a combustion furnace system and a method for burning biomass fuel. Background Art

[0002] Biomass fuel has been attracting attention as a means for reducing the dependence on fossil fuels and suppressing the progress of environmental problems such as global warming. By using biomass fuel instead of fossil fuels, consumption of the fossil fuels can be suppressed.

[0003] In many cases, biomass fuel contains moisture, and therefore needs to be dried before use as fuel. For example, JP 2011-112228 A (Patent Document 1) discloses an invention in which, in a steam boiler using biofuel as fuel, the biofuel is dried by utilizing combustion gas from the steam boiler. Further, JP 2013-47593 A (Patent Document 2) discloses an invention relating to a boiler system that dries biofuel by utilizing waste heat of a boiler device. Citation List Patent Literature

[0004] Patent Document 1: JP 2011-112228 A Patent Document 2: JP 2013-47593 A Summary of Invention Technical Problem

[0005] The inventions of Patent Document 1 and Patent Document 2 adopt configurations in which the biomass fuel after drying is stored and then supplied to a combustion device such as a steam boiler. In these configurations, the stored biomass fuel may absorb moisture again and become unsuitable for combustion.

[0006] Therefore, it is desired to provide a combustion furnace system and a method for burning biomass fuel that can easily ensure that the biomass fuel to be burned is in a state suitable for combustion. Solution to Problem

[0007] A first combustion furnace system according to the present invention includes: a combustion device that uses biomass fuel as fuel; a drying section that dries the biomass fuel; and a supply device that supplies, to the drying section, heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas, wherein the supply device controls at least one of a flow rate or a temperature of the heat medium gas to be supplied to the drying section, based on a moisture content of the biomass fuel.

[0008] A first method for burning biomass fuel according to the present invention includes: a combustion step of burning the biomass fuel; and a drying step of drying the biomass fuel using heat medium gas containing at least one of exhaust gas generated in the combustion step or gas heated by heat exchange with the exhaust gas, wherein at least one of a flow rate or a temperature of the heat medium gas is controlled based on a moisture content of the biomass fuel.

[0009] With these configurations, the degree of drying is adjusted based on the moisture content of the biomass fuel to be supplied to the combustion device, and thus it is easy to ensure that the biomass fuel to be subjected to combustion is in a state suitable for combustion.

[0010] A second combustion furnace system according to the present invention includes: a combustion device that uses biomass fuel as fuel; a storage section that stores the biomass fuel; a drying section that dries the biomass fuel between the storage section and the combustion device; and a supply device that supplies, to the drying section, heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas.

[0011] A second method for burning biomass fuel according to the present invention is a method for burning biomass fuel that burns biomass fuel by using a combustion furnace system including a combustion device that uses biomass fuel as fuel and a storage section that stores the biomass fuel and includes: a drying step of drying the biomass fuel between the storage section and the combustion device by using heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas.

[0012] With these configurations, the biomass fuel is dried while the stored biomass fuel is being supplied to the combustion device, and thus it is easy to ensure that the biomass fuel to be subjected to combustion is in a state suitable for combustion.

[0013] Preferred aspects of the present invention will be described below. However, the scope of the present invention is not limited by the preferred aspects described below.

[0014] In one aspect, the first combustion furnace system according to the present invention preferably further includes a measurement device that measures a moisture content of the biomass fuel to be supplied to the combustion device, wherein the supply device controls at least one of a flow rate or a temperature of the heat medium gas to be supplied to the drying section, based on the moisture content measured by the measurement device.

[0015] With this configuration, the degree of drying is adjusted based on the measured value of the moisture content of the biomass fuel, and thus it is easier to ensure that the biomass fuel to be subjected to combustion is in a state suitable for combustion.

[0016] In one aspect, the first combustion furnace system according to the present invention preferably further includes a storage section that stores the biomass fuel, wherein the drying section is provided between the storage section and the combustion device.

[0017] With this configuration, the biomass fuel is dried while the stored biomass fuel is being supplied to the combustion device, and thus it is easy to ensure that the biomass fuel to be subjected to combustion is in a state suitable for combustion.

[0018] In one aspect of the combustion furnace system according to the present invention, the drying section preferably includes a blowout port through which the heat medium gas is blown out.

[0019] With this configuration, the biomass fuel can be efficiently dried.

[0020] In one aspect of the combustion furnace system according to the present invention, the drying section preferably includes the blowout port at least in a floor surface.

[0021] With this configuration, the heat medium gas can be supplied from below the biomass fuel to be dried, and thus the moisture separated from the biomass fuel is easily removed together with the upward air current. Therefore, the biomass fuel can be dried more efficiently.

[0022] In one aspect, the combustion furnace system according to the present invention preferably further includes a storage device including the storage section and the drying section.

[0023] With this configuration, the storage section and the drying section are provided as an integrated storage device, and thus the installation area of the facility can be reduced.

[0024] Further features and advantages of the present invention will become more apparent from the following description of exemplary and non-limiting embodiments with reference to the drawings. Brief Description of Drawings

[0025] FIG. 1 is a schematic view of a combustion furnace system according to an embodiment. Description of Embodiments

[0026] Embodiments of a combustion furnace system and a method for burning biomass fuel according to the present invention will be described with reference to the drawings. Hereinafter, an example in which the present invention is applied to a combustion furnace system 1 that burns wood chips T (an example of biomass fuel) and a method for burning the wood chips T using the combustion furnace system 1 will be described.

[0027] Configuration of Combustion Furnace System The combustion furnace system 1 according to the present embodiment includes a combustion device 2, a storage device 3, a conveyance device 4, a measurement device 5, a heat utilization device 6, and a supply device 7 (FIG. 1). The combustion furnace system 1 is generally a system in which wood chips T stored in the storage device 3 are burned in the combustion device 2 and combustion heat is used in the heat utilization device 6.

[0028] The combustion device 2 is a combustion device using the wood chips T as fuel, and a known combustion furnace or the like suitable for combustion of the wood chips T can be used. Examples of such a combustion furnace include, but are not limited to, stoker-type and fluidized- bed-type combustion furnaces. Combustion gas generated by the combustion of the wood chips T is sent to the heat utilization device 6 as exhaust gas.

[0029] The storage device 3 is a device that stores the wood chips T used as fuel in the combustion device 2. The storage device 3 includes a storage section 31 functioning as a main space for storing the wood chips T, and a drying section 32 for drying the wood chips T. The storage section 31 and the drying section 32 are obtained by dividing an internal space of the storage device 3 according to the functions of the respective sections, but there is no clear boundary between the two.

[0030] The storage device 3 has, on a floor surface of the internal space, a movable floor 33 for conveying the wood chips T. The movable floor 33 is provided across the storage section 31 and the drying section 32, and conveys the wood chips T in a direction from the storage section 31 toward the drying section 32. In the following description, the front-rear direction of the storage device 3 is defined according to the conveying direction of the wood chips T conveyed by the movable floor 33. That is, the storage section 31 is disposed in a rear portion of the storage device 3, and the drying section 32 is disposed in a front portion of the storage device 3.

[0031] The drying section 32 has, on a floor surface, blowout ports 34 for blowing out heat medium gas described below, and has, on a ceiling, an exhaust fan 35 for discharging the heat medium gas to the outside of the device. In the drying section 32, a flow of the heat medium gas from the blowout ports 34 toward the exhaust fan 35 is formed, and the wood chips T are heated and dried by contact with the heat medium gas. The exhaust fan 35 also serves to discharge moisture (water vapor) separated from the wood chips T to the outside of the device to form an atmosphere conductive to drying of the wood chips T is likely to proceed. The front end of the drying section 32 is connected to the conveyance device 4, and the wood chips T fallen from the front end of the drying section 32 are supplied to the combustion device 2 by the conveyance device 4.

[0032] The wood chips T are conveyed little by little from the rear portion to the front portion in the storage device 3 by the movable floor 33, and then fall from the front end of the drying section 32 to reach the conveyance device 4. The wood chips T received in the storage device 3 from a fuel hopper (not illustrated) are fed into the rear portion of the storage section 31 and are sequentially fed to the drying section 32 by the movable floor 33. The wood chips T are heated by the heat medium gas while passing through the drying section 32, and after being gradually dried, the wood chips T fall from the front end of the drying section 32 to the conveyance device 4.

[0033] The conveyance device 4 is a device that supplies the wood chips T from the storage device 3 to the combustion device 2. As the conveyance device 4, a known device suitable for conveying the wood chips T may be used, and for example, a belt conveyor or the like may be used.

[0034] The measurement device 5 is a device that measures the moisture content of the wood chips T to be supplied to the combustion device 2. In the present embodiment, the measurement device 5 is installed in the conveyance device 4, and measures the moisture content of the wood chips T conveyed by the conveyance device 4. Since the wood chips T reach the conveyance device 4 after being dried in the drying section 32, it can be said that the measurement device 5 measures the moisture content of the wood chips T dried in the drying section 32.

[0035] The heat utilization device 6 is a device that utilizes combustion heat generated by combustion of the wood chips T in the combustion device 2. In an example where the heat utilization device 6 is a boiler and an auxiliary device, the heat utilization device 6 includes a boiler 61, an economizer 62, and a cyclone 63 in this order from the upstream side (the combustion device 2 side). The boiler 61 is a device that heats water by heat exchange with combustion gas (exhaust gas from the combustion device 2) supplied from the combustion device 2 to generate water vapor, and generates the water vapor using combustion heat. The economizer 62 is a device that preheats water by exchanging heat between the combustion gas discharged from the boiler 61 and the water before being supplied to the boiler 61, and is an example of an auxiliary device. The cyclone 63 is a device that collects solids contained in the combustion gas discharged from the economizer 62, and is an example of an auxiliary device. As the boiler 61, the economizer 62, and the cyclone 63, known devices can be used.

[0036] A stack C that discharges the combustion gas (exhaust gas) to the outside of the system and an exhaust pipe P that connects the cyclone 63 and the stack C are provided downstream of the heat utilization device 6 (cyclone 63).

[0037] The supply device 7 is a device that supplies heat medium gas serving as a heat medium for heating the wood chips T in the drying section 32. The supply device 7 includes a heat medium pipe 71 through which the heat medium gas flows, a suction fan 72 that draws air into the heat medium pipe 71, a heat exchanger 73 provided over the heat medium pipe 71 and the exhaust pipe P, a damper 74 provided in the middle of the heat medium pipe 71, and an air supply fan 75 that feeds the heat medium gas to the drying section 32.

[0038] In the present embodiment, air (an example of gas) heated by heat exchange with the exhaust gas from the combustion device 2 is used as the heat medium gas. The air drawn into the heat medium pipe 71 by the suction fan 72 is heated by heat exchange with the exhaust gas flowing through the exhaust pipe P in the heat exchanger 73. The heated air (heat medium gas) is distributed by the damper 74 to a path leading to the drying section 32 via the air supply fan 75 and a path leading to the outside of the system. The heat medium gas that has reached the drying section 32 is blown out from the blowout ports 34. The damper 74 and the air supply fan 75 are electrically connected to the measurement device 5.

[0039] Control of Combustion Furnace System Next, control of the combustion furnace system 1 will be described.

[0040] The combustion furnace or the like used as the combustion device 2 has a different preferred range of the moisture content of the fuel depending on the specification thereof. Therefore, in order to efficiently operate the combustion furnace system 1, it is desired to supply the wood chips T having a moisture content suitable for the specification of the combustion device 2.

[0041] Thus, in the present embodiment, the moisture content of the wood chips T to be supplied to the combustion device 2 is measured by the measurement device 5 provided in the conveyance device 4, and the degree of drying in the drying section 32 is adjusted so that the moisture content becomes an appropriate value in view of the specification of the combustion device 2. Specifically, at least one of the opening degree of the damper 74 or the output of the air supply fan 75 is controlled based on the measured value from the measurement device 5 to control the flow rate of the heat medium gas blown out from the blowout ports 34, thereby adjusting the degree of drying in the drying section 32.

[0042] Other Embodiments Finally, other embodiments of the combustion furnace system and the method for burning biomass fuel according to the present invention will be described. Note that the configuration described in each of the following embodiments can also be applied in combination with the configuration described in another embodiment as long as no contradiction arises.

[0043] In the above embodiment, the configuration in which the air heated by heat exchange with the exhaust gas from the combustion device 2 is used as the heat medium gas has been described as an example. However, as the heat medium gas in the present invention, the exhaust gas itself from the combustion device may be used instead of or in addition to the gas heated by heat exchange with the exhaust gas from the combustion device.

[0044] In the above embodiment, the configuration in which the flow rate of the heat medium gas blown out from the blowout ports 34 is controlled based on the measured value from the measurement device 5 has been described as an example. However, in a first combustion furnace system according to the present invention, the temperature of the heat medium gas may be controlled instead of or in addition to the flow rate of the heat medium gas. In this case, a temperature measurement device that measures the temperature of the heat medium gas may be provided.

[0045] In the above embodiment, the configuration in which the measurement device 5 is installed in the conveyance device 4 has been described as an example. However, the method of determining the moisture content of the biomass fuel in the first combustion furnace system according to the present invention is not limited to the above aspect. For example, a method of estimating the moisture content of the biomass fuel from the past operation record of the combustion furnace system, a method of using the value of the moisture content measured in advance outside the combustion furnace system, and the like are exemplified. Therefore, the first combustion furnace system according to the present invention may include a means corresponding to the method of determining the moisture content, and the measurement device is merely an example thereof. In addition, in the case where the measurement device is provided, the position thereof is not limited as long as the position is a position where the moisture content of the biomass fuel to be supplied to the combustion device can be measured. The measurement device may thus be provided, for example, at the inlet of the biomass fuel in the combustion device or, in a configuration in which a storage section is provided, at the outlet of the storage section.

[0046] In the above embodiment, the configuration including the storage device 3 including the storage section 31 and the drying section 32 has been described as an example. However, in a second combustion furnace system according to the present invention, the storage section and the drying section may be incorporated in an integrated device or may be present as separate devices.

[0047] In the above embodiment, the configuration in which the blowout ports 34 are provided in the floor surface of the drying section 32 and the wood chips T are dried by the heat medium gas blown from the blowout ports 34 has been described as an example. However, in the present invention, the method of drying the biomass fuel using the heat medium gas is not limited.

[0048] In the above embodiment, the configuration in which the wood chips T are used as the biomass fuel has been described as an example. However, the biomass fuel used in the present invention is not limited to wood chips. Examples of the biomass fuel include food residues (coffee grounds, spent grain, spent green tea leaves, sake lees, pomace from grapes and other fruits, and the like). The specifications of the combustion device, the drying section, and the like may be changed as appropriate according to the properties and the like of the biomass fuel to be used.

[0049] Also, with respect to other configurations, it should be understood that the embodiments described in the present specification are illustrative in all respects and that the scope of the present invention is not limited thereto. It will be easily understood by those skilled in the art that appropriate modifications can be made without departing from the spirit of the present invention. Accordingly, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention. Examples

[0050] Hereinafter, the present invention will be further described with reference to examples. However, the following examples do not limit the present invention.

[0051] Test Device As a jet heater for generating hot air, a hot gun HGDHII-T (manufactured by Shizuoka Seiki Co., Ltd.) was used. As an air supply fan for blowing hot air to wood chips, EBARA FAN No. 3 APM (manufactured by EBARA CORPORATION) was used. As a moisture content measurement device, humimeter BLL (manufactured by BEA Institut fuer Bioenergie GmbH) was used.

[0052] Example 1 The wood chips were dried by blowing hot air at 40 °C from the side of a sample pile in which the wood chips were stacked to a height of approximately 1.5 m. One air supply fan was used. The moisture content of the wood chips was measured before the start of drying and every 30 minutes during drying. The measurement of the moisture content was performed by collecting samples from three points at different heights in the sample pile, and the average value of the moisture content at the three points was used as the measured value. The above test was performed until 150 minutes after the start of drying.

[0053] Example 2 A test was performed in the same manner as in Example 1 except that hot air was blown from below the sample pile in addition to blowing hot air from the side of the sample pile. The hot air was supplied from below the sample pile by connecting a vinyl-chloride-made pipe having blowout ports with a diameter of 70 mm on the side surface to an air supply fan and inserting a 1 m portion of the pipe below the sample pile. The number of blowout ports provided in the portion inserted under the sample pile was seven, and the number of air supply fans used was two.

[0054] Test Results Table 1 shows the test results of Example 1 and Example 2. In both examples, the moisture content of the wood chips decreased with the passage of time. The decrease in the moisture content was particularly significant in Example 2 in which hot air was supplied from both the side of and below the sample pile.

[0055] Table 1: Examples [Table 1] 0 min 30 min 60 min 90 min 120 min 150 min Example 1 31.5 29.7 28.0 27.2 26.5 26.4 Example 2 32.1 26.3 20.8 18.9 15.9 12.7 (The numerical values in the table are average moisture content [%]) Industrial Applicability

[0056] The present invention can be used as a combustion furnace system using wood chips as fuel and a method of operating the same, for example. Reference Signs List

[0057] 1: Combustion furnace system 2: Combustion device 3: Storage device 31: Storage section 32: Drying section 33: Movable floor 34: Blowout port 35: Exhaust fan 4: Conveyance device 5: Measurement device 6: Heat utilization device 61: Boiler 62: Economizer 63: Cyclone 7: Supply device 71: Heat medium pipe 72: Suction fan 73: Heat exchanger 74: Damper 75: Air supply fan T: Wood chip C: Stack P: Exhaust pipe

Claims

1. A combustion furnace system comprising:a combustion device configured to use biomass fuel as fuel;a drying section configured to dry the biomass fuel; anda supply device configured to supply, to the drying section, heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas, whereinthe supply device controls at least one of a flow rate or a temperature of the heat medium gas to be supplied to the drying section, based on a moisture content of the biomass fuel.

2. A combustion furnace system comprising:a combustion device configured to use biomass fuel as fuel;a storage section configured to store the biomass fuel;a drying section configured to dry the biomass fuel between the storage section and the combustion device; anda supply device configured to supply, to the drying section, heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas.

3. The combustion furnace system according to claim 1, further comprising a measurement device configured to measure a moisture content of the biomass fuel to be supplied to the combustion device, whereinthe supply device controls at least one of a flow rate or a temperature of the heat medium gas to be supplied to the drying section, based on the moisture content measured by the measurement device.

4. The combustion furnace system according to claim 1, further comprising a storage section configured to store the biomass fuel, whereinthe drying section is provided between the storage section and the combustion device.The combustion furnace system according to any one of claims 1 to 4, wherein the drying section includes a blowout port through which the heat medium gas is blown out.

6. The combustion furnace system according to claim 5, wherein the drying section includes the blowout port at least in a floor surface.

7. The combustion furnace system according to claim 2 or 4, further comprising a storage device including the storage section and the drying section.

8. A method for burning biomass fuel, the method comprising:a combustion step of burning the biomass fuel; anda drying step of drying the biomass fuel using heat medium gas containing at least one of exhaust gas generated in the combustion step or gas heated by heat exchange with the exhaust gas, whereinat least one of a flow rate or a temperature of the heat medium gas is controlled based on a moisture content of the biomass fuel.

9. A method for burning biomass fuel that burns biomass fuel by using a combustion furnace system including a combustion device configured to use the biomass fuel as fuel and a storage section configured to store the biomass fuel, the method comprising:a drying step of drying the biomass fuel between the storage section and the combustion device by using heat medium gas containing at least one of exhaust gas from the combustion device or gas heated by heat exchange with the exhaust gas.

Images