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

Combustion furnace system and method for burning biomass fuel

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

[0002] Biomass fuels are attracting attention as a means of reducing dependence on fossil fuels and curbing the progression of environmental problems such as global warming. By using biomass fuels instead of fossil fuels, we can reduce fossil fuel consumption.

[0003] In many cases, biomass fuels contain moisture and therefore need to be dried before being used as fuel. For example, Japanese Patent Laid-Open Publication No. 2011-112228 (Patent Document 1) discloses an invention in which a steam boiler that uses biofuel as fuel dries the biofuel by utilizing combustion gas from the steam boiler. Also, Japanese Patent Laid-Open Publication No. 2013-47593 (Patent Document 2) discloses an invention related to a boiler system that dries biofuel by utilizing waste heat from a boiler device.

[0004] JP 2011-112228 A JP 2013-47593 A

[0005] The inventions of Patent Documents 1 and 2 employ a configuration in which dried biomass fuel is stored and then supplied to a combustion device such as a steam boiler. In these configurations, there is a risk that the stored biomass fuel will absorb moisture again, making it unsuitable for combustion.

[0006] Therefore, it is desirable to realize 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.

[0007] The first combustion furnace system according to the present invention comprises a combustion device that uses biomass fuel as fuel, a drying section that dries the biomass fuel, and a supply device that supplies a heat transfer gas containing at least one of exhaust from the combustion device and gas heated by heat exchange with the exhaust to the drying section, and is characterized in that the supply device controls at least one of the flow rate and temperature of the heat transfer gas supplied to the drying section based on the moisture content of the biomass fuel.

[0008] The first biomass fuel combustion method according to the present invention comprises a combustion process for burning biomass fuel, and a drying process for drying the biomass fuel using a heat transfer gas containing at least one of exhaust gas generated in the combustion process and gas heated by heat exchange with the exhaust gas, and is characterized in that at least one of the flow rate and temperature of the heat transfer gas is controlled based on the moisture content of the biomass fuel.

[0009] According to these configurations, the degree of dryness is adjusted based on the moisture content of the biomass fuel supplied to the combustion device, making it easier to ensure that the biomass fuel being burned is in a state suitable for combustion.

[0010] The second combustion furnace system according to the present invention is characterized by comprising 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 a heat transfer gas containing at least one of exhaust from the combustion device and a gas heated by heat exchange with the exhaust to the drying section.

[0011] The second biomass fuel combustion method of the present invention is a method for burning biomass fuel using a combustion furnace system including a combustion device that uses biomass fuel as fuel and a storage unit that stores the biomass fuel, and is characterized by including a drying step between the storage unit and the combustion device, in which the biomass fuel is dried using a heat transfer gas that includes at least one of exhaust from the combustion device and a gas heated by heat exchange with the exhaust.

[0012] According to these configurations, the stored biomass fuel is dried while it is being supplied to the combustion device, making it easier to ensure that the biomass fuel being burned is in a state suitable for combustion.

[0013] Preferred embodiments of the present invention will be described below, but the scope of the present invention is not limited to the preferred embodiments described below.

[0014] In one aspect, the first combustion furnace system according to the present invention further comprises a measuring device that measures the moisture content of the biomass fuel supplied to the combustion device, and it is preferable that the supply device controls at least one of the flow rate and temperature of the heat transfer gas supplied to the drying section based on the moisture content measured by the measuring device.

[0015] According to this configuration, the degree of dryness is adjusted based on the measured moisture content of the biomass fuel, making it easier to ensure that the biomass fuel to be burned is in a state suitable for combustion.

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

[0017] According to this configuration, the stored biomass fuel is dried while it is being supplied to the combustion device, making it easier to ensure that the biomass fuel being burned 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 has an outlet through which the heat transfer gas is blown out.

[0019] This configuration allows the biomass fuel to be dried efficiently.

[0020] In one aspect of the combustion furnace system according to the present invention, the drying section preferably has the air outlet on at least a floor surface.

[0021] With this configuration, the heat transfer gas can be supplied from below the biomass fuel to be dried, which makes it easier for moisture released from the biomass fuel to be removed along with the rising air current, thereby enabling the biomass fuel to be dried more efficiently.

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

[0023] According to this configuration, the storage section and the drying section are provided as an integrated storage device, so that the installation area of ​​the equipment 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, which is given with reference to the drawings.

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

[0026] An embodiment 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. In the following, 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 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 this embodiment includes a combustion device 2, a storage device 3, a transport device 4, a measurement device 5, a heat utilization device 6, and a supply device 7 ( FIG. 1 ). Generally, the combustion furnace system 1 is a system in which wood chips T stored in the storage device 3 are combusted in the combustion device 2 and the combustion heat is utilized in the heat utilization device 6.

[0028] The combustion device 2 is a combustion device that uses wood chips T as fuel, and may be a known combustion furnace or the like that is suitable for burning wood chips T. Examples of such combustion furnaces include, but are not limited to, stoker-type and fluidized bed-type combustion furnaces. The 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 wood chips T to be used as fuel in the combustion device 2. The storage device 3 has a storage section 31 that functions as the main space for storing the wood chips T, and a drying section 32 that dries the wood chips T. Note that the storage section 31 and the drying section 32 are sections of the internal space of the storage device 3 that are divided according to function, but there is no clear boundary between them.

[0030] The storage device 3 also has a movable floor 33 on the floor surface of its internal space for transporting wood chips T. The movable floor 33 is provided across the storage section 31 and the drying section 32, and transports the wood chips T in the direction from the storage section 31 to the drying section 32. Hereinafter, the front-rear direction of the storage device 3 will be defined according to the transport direction of the wood chips T by the movable floor 33. In other words, the storage section 31 is located behind the storage device 3, and the drying section 32 is located in front of the storage device 3.

[0031] The drying section 32 has an outlet 34 on the floor through which a heat transfer gas (described later) is blown out, and an exhaust fan 35 on the ceiling that exhausts the heat transfer gas to the outside of the device. In the drying section 32, a flow of heat transfer gas is formed from the outlet 34 toward the exhaust fan 35, and the wood chips T are heated and dried by contact with the heat transfer gas. The exhaust fan 35 also serves to exhaust moisture (water vapor) released from the wood chips T to the outside of the device, creating an atmosphere that facilitates drying of the wood chips T. The front end of the drying section 32 is connected to the conveying device 4, and the wood chips T that drop from the front end of the drying section 32 are supplied to the combustion device 2 by the conveying device 4.

[0032] The wood chips T are transported little by little from the rear to the front of the storage device 3 by the movable floor 33, and eventually drop from the front end of the drying section 32 to reach the conveying device 4. The wood chips T received in the storage device 3 from a fuel hopper (not shown) are fed into the rear part of the storage section 31 and are sequentially sent to the drying section 32 by the movable floor 33. The wood chips T are heated by the heat transfer gas while passing through the drying section 32, and are gradually dried before dropping from the front end of the drying section 32 into the conveying device 4.

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

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

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

[0036] Downstream of the heat utilization device 6 (cyclone 63), a chimney C for discharging combustion gas (exhaust gas) to the outside of the system and an exhaust pipe P connecting the cyclone 63 and the chimney C are provided.

[0037] The supply device 7 is a device that supplies heat medium gas that serves as a heat medium for heating the wood chips T in the drying section 32. The supply device 7 has 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 that is provided between the heat medium pipe 71 and the exhaust pipe P, a damper 74 that is provided midway through the heat medium pipe 71, and an air supply fan 75 that sends the heat medium gas to the drying section 32.

[0038] In this embodiment, air (one example of a gas) heated by heat exchange with exhaust gas from the combustion device 2 is used as the heat transfer gas. Air drawn into the heat transfer pipe 71 by the suction fan 72 is heated in the heat exchanger 73 by heat exchange with exhaust gas flowing through the exhaust pipe P. The heated air (heat transfer gas) is distributed by a damper 74 into a path that passes through the air supply fan 75 and reaches the drying section 32, and a path that exits the system. The heat transfer gas that reaches the drying section 32 is blown out from the outlet 34. The damper 74 and the air supply fan 75 are electrically connected to the measuring device 5.

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

[0040] The optimum range of moisture content of fuel varies depending on the specifications of the combustion furnace or the like used as the combustion device 2. Therefore, in order to operate the combustion furnace system 1 efficiently, it is desirable to supply wood chips T with a moisture content that is suitable for the specifications of the combustion device 2.

[0041] Therefore, in this embodiment, the moisture content of the wood chips T supplied to the combustion device 2 is measured by the measuring device 5 provided on the transport device 4, and the degree of drying in the drying section 32 is adjusted so that the moisture content becomes an appropriate value in consideration of the specifications of the combustion device 2. Specifically, based on the measurement value of the measuring device 5, at least one of the opening degree of the damper 74 and the output of the air supply fan 75 is controlled to control the flow rate of the heat transfer gas blown out from the outlet 34, thereby adjusting the degree of drying in the drying section 32.

[0042] [Other Embodiments] Finally, other embodiments of the combustion furnace system and biomass fuel combustion method according to the present invention will be described. Note that the configurations disclosed in the following embodiments can be applied in combination with the configurations disclosed in other embodiments, as long as no contradiction occurs.

[0043] In the above embodiment, an example has been described in which the heat transfer gas is air heated by heat exchange with the exhaust gas from the combustion device 2. However, the heat transfer gas in the present invention may be the exhaust gas from the combustion device itself, 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, an example has been described in which the flow rate of the heat transfer gas blown out from the outlet 34 is controlled based on the measurement value of the measuring device 5. However, in the first combustion furnace system according to the present invention, the temperature of the heat transfer gas may be controlled instead of or in addition to the flow rate of the heat transfer gas. In this case, a temperature measuring device for measuring the temperature of the heat transfer gas may be provided.

[0045] In the above embodiment, the measuring device 5 is installed on the transport device 4. However, the method for determining the moisture content of biomass fuel in the first combustion furnace system according to the present invention is not limited to the above. For example, a method for estimating the moisture content of biomass fuel from the past operating data of the combustion furnace system or a method for using a moisture content value measured in advance outside the combustion furnace system are examples. Therefore, the first combustion furnace system according to the present invention is only required to include a means for determining the moisture content, and the measuring device is merely one example. Furthermore, if a measuring device is installed, its location is not limited as long as it is a location that can measure the moisture content of the biomass fuel supplied to the combustion device. Therefore, the measuring device may be installed, for example, at the inlet of the biomass fuel in the combustion device, or at the outlet of the storage unit in a configuration where a storage unit is installed.

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

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

[0048] In the above embodiment, an example has been described in which wood chips T are used as biomass fuel. However, the biomass fuel used in the present invention is not limited to wood chips. Examples of biomass fuel include food waste (coffee grounds, barley dregs, green tea dregs, sake lees, grape and other fruit pomace, etc.). Specifications of the combustion device, drying unit, etc. can be changed as appropriate depending on the properties of the biomass fuel used.

[0049] Regarding other configurations, it should be understood that the embodiments disclosed in this specification are illustrative in all respects and that the scope of the present invention is not limited thereby. Those skilled in the art will easily understand that appropriate modifications are possible without departing from the spirit of the present invention. Therefore, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

[0050] The present invention will be further described below by way of examples, but the present invention is not limited to these examples.

[0051] [Test equipment] A hot gun HGDHII-T (manufactured by Shizuoka Seiki Co., Ltd.) was used as a jet heater that generates hot air. An EBARA FAN No. 3 APM (manufactured by Ebara Corporation) was used as an air blower that sends hot air to the wood chips. A Humimeter BLL (manufactured by BEA Institut für Bioenergie GmbH) was used as a moisture content measuring device.

[0052] Example 1 Wood chips were piled up to a height of approximately 1.5 m, and hot air at 40°C was blown onto the side of the sample block to dry the wood chips. 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. Moisture content measurements were performed by taking samples from three different heights on the sample block, and the average moisture content of the three points was used as the measured value. The above test was performed for 150 minutes from the start of drying.

[0053] Example 2 A test was conducted in the same manner as in Example 1, except that in addition to blowing hot air from the side of the sample block, hot air was also blown from below the sample block. Hot air was supplied from below the sample block by connecting a vinyl chloride pipe with a 70 mm diameter outlet on the side to an air supply fan, and inserting a 1 m length of the pipe below the sample block. There were seven air supply outlets in the part inserted below the sample block, and two air supply fans were used.

[0054] [Test Results] The test results for Examples 1 and 2 are shown in Table 1. In both examples, the moisture content of the wood chips decreased over time. The decrease in moisture content was particularly significant in Example 2, in which hot air was supplied from the sides and below the test block.

[0055] Table 1: Examples

[0056] The present invention can be used, for example, in a combustion furnace system that uses wood chips as fuel and a method for operating the same.

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

Claims

1. A combustion furnace system comprising: a combustion device that uses biomass fuel as fuel; a drying section that dries the biomass fuel; and a supply device that supplies a heat transfer gas to the drying section, the heat transfer gas including at least one of exhaust from the combustion device and gas heated by heat exchange with the exhaust, wherein the supply device controls at least one of the flow rate and the temperature of the heat transfer gas supplied to the drying section based on the moisture content of the biomass fuel.

2. A combustion furnace system comprising: 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 a heat transfer gas containing at least one of exhaust from the combustion device and a gas heated by heat exchange with the exhaust to the drying section.

3. The combustion furnace system of claim 1, further comprising a measuring device for measuring the moisture content of the biomass fuel supplied to the combustion device, and the supply device controls at least one of the flow rate and temperature of the heat transfer gas supplied to the drying section based on the moisture content measured by the measuring device.

4. The combustion furnace system according to claim 1, further comprising a storage section for storing the biomass fuel, and the drying section is provided between the storage section and the combustion device.

5. A combustion furnace system according to any one of claims 1 to 4, wherein the drying section has an outlet through which the heat transfer gas is blown out.

6. The combustion furnace system according to claim 5, wherein the drying section has the outlet at least on the floor surface.

7. A combustion furnace system according to claim 2 or 4, comprising a storage device having said storage section and said drying section.

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

9. A method for burning biomass fuel by using a combustion furnace system including a combustion device that uses biomass fuel as fuel and a storage unit that stores the biomass fuel, the method including a drying step of drying the biomass fuel between the storage unit and the combustion device using a heat transfer gas that includes at least one of exhaust from the combustion device and a gas heated by heat exchange with the exhaust.

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