JP2005048967A - Pulverulent fuel combustion device and pulverulent fuel combustion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To pulverize wood flour adequately finely and dry it while preventing dew condensation of a sulfur content and ignition of a wooden material in a mill even when the wood flour is used as fuel. <P>SOLUTION: A mill 11 pulverizes a wooden material and dries it by a drying air stream to generate wood flour, and discharges the wood flour to the outside together with exhaust gas S1. A dust collector 12 collects the wood flour carried by the exhaust gas S1 and discharges exhaust gas S6 while removing the wood flour from the exhaust gas S1. A boiler 14 burns this wood flour as fuel and discharges exhaust gas S3. A controlling part 30 mixes a part S3' of the exhaust gas S3 and a part S6' of the exhaust gas S6 in an appropriate mixing ratio based on a detection signal of a temperature sensor 31 installed near an exit of the exhaust gas S1 in the mill 11, thereby maintaining the temperature of the exhaust gas S1 at 110 °C to 130 °C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulverized fuel combustion apparatus and a pulverized fuel combustion method in which a solid fuel is finely pulverized and simultaneously dried to obtain a pulverized fuel.
[0002]
[Prior art]
In response to the increasing demand for energy in recent years, pulverized coal produced by crushing and drying coal containing a lot of moisture and volatiles such as brown coal instead of high-grade coal such as bituminous coal In addition, development of a pulverized fuel combustion apparatus using pulverized fuel such as wood powder obtained by pulverizing and drying wood into a powder form is underway.
[0003]
As what discloses such a pulverized fuel combustion apparatus, for example, one disclosed in Patent Document 1 is known. In this Patent Document 1, for example, as shown in FIGS. 4 and 5, the finely pulverized fuel pulverized and dried by the mill 11 is transferred to the dust collector 12 and collected together with the exhaust gas S1, and then stored in the silo 12 ′. The The pulverized fuel stored in the silo 12 ′ is supplied to the boiler 14 by the conveying airflow S 2 generated by the blower 13. Exhaust gas S3 from the boiler 14 passes through the air heater 15. The air heater 15 absorbs the heat energy of the exhaust gas S3 and applies this heat energy to the airflow S4 generated by the blower 16 and given to the boiler 14 for combustion. The exhaust gas S3 from the boiler 14 whose temperature has been lowered by the air heater 15 is collected by the dust collector 17, desulfurized by the desulfurizer 18, and then discharged from the chimney 19 to the atmosphere. The mill 11 needs to be fed with a drying airflow for drying the pulverized fuel. In Patent Document 1, an example (FIG. 4) in which a part of an airflow S4 ′ generated by heating an airflow S4 with an air heater 15 is sent to a mill 11 as a drying airflow, and an exhaust gas S5 after passing through a dust collector 17 is used for drying. An example of sending air to the mill 11 as an air flow (FIG. 5) is disclosed.
[0004]
[Patent Document 1]
Japanese Examined Patent Publication No. 62-55057 (right column of page 1 to page 2, FIGS. 1 and 2)
[0005]
[Problems to be solved by the invention]
However, the configuration disclosed in Patent Document 1 has no problem when pulverized coal is used as a fuel, but has more moisture and volatile components than pulverized coal and uses wood powder having a low ignition temperature as a fuel. Therefore, there arises a problem that pulverization and drying cannot be performed sufficiently. That is, in the configuration of FIG. 4, since the air flow S4 ′ is an air flow having a large oxygen component, such a high oxygen concentration air flow is inappropriate for pulverization and drying of wood powder having a low ignition temperature (coal While the ignition temperature is about 300 to 500 degrees, the ignition temperature of wood flour is around 260 ° C.).
In the case of FIG. 5, the temperature of the exhaust gas S5 exiting from the dust collector 17 is normally 150 ° C. or lower. Although this temperature is sufficiently high for drying pulverized coal, it is not sufficient for pulverizing and drying wood powder with higher moisture content. When such a low temperature exhaust gas is used as a drying airflow, not only the wood cannot be sufficiently pulverized and dried, but the temperature of the exhaust gas discharged from the mill 11 is further lowered. Consequently, sulfur components in the exhaust gas may be condensed inside the mill 11 or in the exhaust pipe, which may cause corrosion and clogging of the apparatus and the exhaust pipe.
The present invention has been made in view of such problems. Even when wood powder is used as a fuel, the wood powder is produced while preventing ignition in a wood mill, condensation of sulfur components, and the like. It is an object of the present invention to provide a pulverized fuel combustion apparatus and a pulverized fuel combustion method that can be sufficiently finely pulverized and dried.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a pulverized fuel combustion apparatus according to the present invention includes a pulverizing and drying apparatus that pulverizes a solid fuel and dries it with a drying airflow to generate pulverized fuel and discharges it together with a first exhaust gas. A pulverized fuel collector that collects the pulverized fuel transported by the first exhaust gas from an apparatus and discharges the second exhaust gas generated by removing the pulverized fuel from the first exhaust gas; and A boiler that discharges the third exhaust gas by burning pulverized fuel as fuel, and the temperature of the drying air flow is adjusted so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C. And an airflow introduction unit for drying introduced into the pulverizing and drying apparatus.
[0007]
According to the present invention, the temperature of the drying airflow is adjusted so that the temperature of the first exhaust gas is 110 ° C to 130 ° C. As a result, even when wood powder is used as fuel, dew condensation of sulfur components in the first exhaust gas is prevented, and the wood is pulverized sufficiently finely while preventing ignition in the wood mill. And can be dried.
[0008]
The pulverized fuel combustion method according to the present invention includes a pulverization and drying step in which solid fuel is pulverized and dried by an air flow for drying to generate pulverized fuel and transported with the first exhaust gas, and the first exhaust gas transports A pulverized fuel collecting step of collecting the pulverized fuel and discharging the second exhaust gas generated by removing the pulverized fuel from the first exhaust gas; and A combustion step for exhausting exhaust gas and a drying step for adjusting the temperature of the drying air flow so that the temperature of the first exhaust gas is 110 ° C. to 130 ° C. and introducing the drying air flow into the pulverization drying device An air flow introduction step.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the pulverized fuel combustion apparatus according to the first embodiment of the present invention. The same elements as those of the conventional pulverized fuel combustion apparatus (FIGS. 4 and 5) are denoted by the same reference numerals, and detailed description thereof is omitted. The characteristic point in the present embodiment is that the mill 11 has an inert gas having a low oxygen concentration (oxygen concentration of 2 to 5%) discharged from an ECO 14 ′ (Economizer: economizer) provided at the outlet of the boiler 14. ) Part of the exhaust gas S3 and part of the exhaust gas S6 exhausted from the dust collector 12 are mixed to form a mixed gas S7, and this mixed gas S7 is used as a drying airflow through the transport pipe 21. It is introduced into the mill 11.
[0010]
As described above, the exhaust gas S3 ′ has a low oxygen concentration and a temperature of about 350 ° C., while the exhaust gas S6 ′ is about 110 to 130 ° C. The mixing ratio of the exhaust gases S3 ′ and S6 ′ is adjusted so that the temperature of the exhaust gas S1 discharged from the mill 11 is about 110 to 130 ° C., and the oxygen concentration of the mixed gas S7 is about 3 to 10% (preferably Is maintained at about 7%). As shown in FIG. 1, in this embodiment, a control unit 30 and a temperature sensor 31 are provided, and thereby the temperature of the exhaust gas S1 is controlled. That is, the temperature sensor 31 disposed in the vicinity of the outlet of the exhaust gas S1 of the mill 11 detects the temperature of the exhaust gas S1, and based on this detection signal, the control unit 30 detects the branch damper DD and the blower 20 at the outlet of the blower 13 ′. And the supply ratio of the exhaust gases S3 ′ and S6 ′ from the blower 13 ′ and the blower 20 is changed. Thereby, the temperature of the exhaust gas S1 is maintained at about 110 to 130 ° C., thereby preventing condensation of sulfur components in the mill 11 and the exhaust pipe, and preventing corrosion and clogging of the inside of the mill 11 and the exhaust pipe. However, the wood flour can be dried to a moisture content of, for example, about 5 to 8% and conveyed by an air stream, and can be finely pulverized to such an extent that sufficient combustion efficiency in the boiler 14 can be obtained. Further, since both the exhaust gases S3 ′ and S6 ′ have a low oxygen concentration, the oxygen concentration in the mill 11 can be kept low, thereby preventing ignition of wood powder in the mill 11. Further, the control unit 30 branches the outlet of the blower 13 ′ so that the total supply amount of the exhaust gases S3 ′ and S6 ′ is sufficient to produce wood powder from the mill 11 and transport it to the dust collector 12. The damper DD and the blower 20 are controlled.
[0011]
The ratio of the exhaust gas S6 ′ introduced into the mill 11 to the exhaust gas S6 may be about 60 to 85%, and the rest is discharged into the atmosphere by the blower 13 ′. This numerical value fluctuates based on the temperature change of the exhaust gas S1.
Further, instead of the dust collector 12 and the silo 12 ', as shown in FIG. 2, fine wood powder and coarse wood powder are classified, and only the classified fine wood powder is transported to the boiler 14 by the transport air current from the blower 13. A cyclone 23 can also be provided. In this case, as in FIG. 1, a part S6 ′ of the exhaust gas S6 from the cyclone 23 is sent to the transport pipe 21 via the branch damper DD at the outlet of the blower 13 ′ and mixed with the exhaust gas S3 ′. Also in FIG. 2, the ratio of the exhaust gas S6 ′ to the exhaust gas S6 may be about 60 to 85%, and the remainder is supplied to the boiler 14 by the blower 13 ′. In FIG. 2, by introducing the remaining gas into the boiler 14, a dust collector for discharging the cyclone exhaust gas into the atmosphere becomes unnecessary.
The mill 11 is typically a vertical roller mill, but any type can be used as long as the solid fuel can be pulverized, such as a ball mill or a cutter mill. In addition, when wood powder is used as a fuel, fuel with a large calorific value such as pulverized coal can be separately supplied by a supply route (not shown), and the wood powder and pulverized coal can be mixed and burned.
[0012]
FIG. 3 illustrates a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the first embodiment, as the drying airflow, a part S3 ′ of the low oxygen concentration exhaust gas S3 exhausted from the ECO 14 ′ of the boiler 14 and a part S6 ′ of the exhaust gas S6 exhausted from the dust collector 12 are used. Was introduced into the mill 11 via the branch damper DD at the outlet of the blower 13 ′, the blower 20, and the transport pipe 21. On the other hand, in the second embodiment, the transport pipe 21, the blower 20, and the like are not provided, but instead, a hot air generating furnace 22 that combusts fuel and generates exhaust gas S8 having a low oxygen concentration is provided. An exhaust gas S9 generated by mixing the gas S8 with the exhaust gas S6 'is introduced into the mill 11 as a drying airflow. The hot air generating furnace 22 is configured to be able to adjust the temperature of the exhaust gas S8 to be generated, and the control unit 30 performs the adjustment based on a detection signal from the temperature sensor 31. The control unit 30 controls the hot air generating furnace 22 so that the temperature of the exhaust gas S1 from the mill 11 is about 110 to 130 ° C. Thereby, dew condensation of sulfur components at the outlet of the mill 11 can be prevented, and corrosion and clogging of the inside of the mill 11 and the exhaust pipe can be prevented.
[0013]
Although the embodiments of the invention have been described above, the present invention is not limited to these embodiments, and various design changes can be made without departing from the spirit of the present invention.
[0014]
【The invention's effect】
As described above, according to the pulverized fuel combustion apparatus and the pulverized fuel combustion method according to the present invention, even when wood powder is used as fuel, it is possible to prevent condensation of sulfur, ignition in a wood mill, and the like. However, the wood flour can be sufficiently finely pulverized and dried.
[Brief description of the drawings]
FIG. 1 shows the overall configuration of a pulverized fuel combustion apparatus according to a first embodiment of the present invention.
FIG. 2 shows a modification of the first embodiment.
FIG. 3 shows an overall configuration of a pulverized fuel combustion apparatus according to a second embodiment of the present invention.
FIG. 4 shows the overall configuration of a pulverized fuel combustion apparatus according to the prior art.
FIG. 5 shows the overall configuration of a pulverized fuel combustion apparatus according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Mill, 12 ... Dust collector, 12 '... Silo, 13, 13' ... Blower, 14 ... Boiler, 14 '... ECO, 15 ... Air heater, 16 ... -Blower, 17 ... Dust collector, 18 ... Desulfurization device, 19 ... Chimney, 20 ... Blower, 21 ... Conveying pipe, 22 ... Hot air generator, 23 ... Cyclone, 30 ..Control unit 31 ... Temperature sensor.

Claims (8)

A pulverizing and drying device for pulverizing solid fuel and drying it with an air flow for drying to produce finely pulverized fuel and discharging it together with the first exhaust gas;
A pulverized fuel collector that collects the pulverized fuel conveyed by the first exhaust gas from the pulverizing and drying apparatus and discharges the second exhaust gas generated by removing the pulverized fuel from the first exhaust gas. When,
A boiler that discharges the third exhaust gas by burning the pulverized fuel as fuel;
A drying air flow introducing section for adjusting the temperature of the drying air flow and introducing the drying air flow into the pulverization drying device so that the temperature of the first exhaust gas is 110 ° C. to 130 ° C. A pulverized fuel combustion device. The drying air flow introduction unit mixes the second exhaust gas and the third exhaust gas to generate a mixed gas, and introduces the mixed gas into the pulverization drying apparatus as the drying air flow. The pulverized fuel combustion apparatus according to claim 1. A hot air generating furnace for generating fourth exhaust gas;
The drying air flow introduction unit mixes the second exhaust gas and the fourth exhaust gas to generate a mixed gas, and introduces the mixed gas into the pulverization drying apparatus as the drying air flow. The pulverized fuel combustion apparatus according to claim 1. The pulverized fuel combustion apparatus according to any one of claims 1 to 3, further comprising a pulverized fuel storage unit that stores the pulverized fuel collected by the pulverized fuel collection unit. The pulverized fuel combustion apparatus according to any one of claims 1 to 4, wherein the drying airflow is an inert gas having an oxygen concentration of 3 to 10%. A pulverizing and drying step of pulverizing the solid fuel and drying it with a drying airflow to produce a finely divided fuel and transporting it together with the first exhaust gas;
A pulverized fuel collecting step of collecting the pulverized fuel conveyed by the first exhaust gas and discharging a second exhaust gas generated by removing the pulverized fuel from the first exhaust gas;
A combustion step of combusting the pulverized fuel with the boiler and discharging a third exhaust gas;
A drying airflow introducing step of adjusting the temperature of the drying airflow and introducing the drying airflow into the pulverization drying device so that the temperature of the first exhaust gas is 110 ° C to 130 ° C. A pulverized fuel combustion method. 7. The drying air flow introducing step generates the mixed gas by mixing the second exhaust gas and the third exhaust gas, and uses the mixed gas as the drying air flow. Pulverized fuel combustion method. Further comprising generating a fourth exhaust gas,
The drying air flow introducing step mixes the second exhaust gas and the fourth exhaust gas to generate a mixed gas, and introduces the mixed gas into the pulverization drying apparatus as the drying air flow. The pulverized fuel combustion method according to claim 6.

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