JP4378402B2 - Wood powder fuel combustion apparatus and wood powder fuel combustion method - Google Patents

Description

The present invention relates to a wood powder fuel combustion apparatus and a wood powder fuel combustion method using a solid fuel finely pulverized and simultaneously dried to obtain a fine powder fuel , which is used as the fuel.

  In response to the increasing demand for energy in recent years, pulverized coal produced by pulverizing and drying coal containing a lot of moisture and volatiles such as lignite 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.

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.
Japanese Examined Patent Publication No. 62-55057 (right column of page 1 to page 2, FIGS. 1 and 2)

  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. and to provide a sufficiently finely ground and dried wood flour fuel combustion apparatus Ru can cause and wood powder fuel combustion method.

In order to achieve the above object, a wood powder fuel combustion apparatus according to the present invention includes a wood grinding and drying apparatus that pulverizes wood and dries it with an air flow for drying to produce wood powder fuel and discharges it together with the first exhaust gas. A boiler for burning wood powder fuel as fuel and discharging combustion exhaust gas; a control means for controlling the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C .; Collecting the wood powder fuel transported by the first exhaust gas from the wood grinding and drying device and removing the wood fuel from the first exhaust gas between the wood grinding and drying device and the boiler And the wood gas fuel collecting part for discharging the second exhaust gas, and the drying airflow mixes the second exhaust gas and the combustion exhaust gas to generate a mixed gas, As the air flow for drying And introducing the wood grinding drying apparatus.
In addition, another wood powder fuel combustion apparatus according to the present invention includes a wood grinding and drying apparatus that pulverizes wood and dries it with a drying airflow to generate wood powder fuel and discharges it together with the first exhaust gas, and the wood powder. A boiler that burns fuel as fuel and discharges combustion exhaust gas; a control means that controls the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C .; The wood powder fuel transported by the first exhaust gas from the wood crushing and drying device is collected between the drying device and the boiler, and is generated by removing the wood powder fuel from the first exhaust gas. A wood powder fuel collecting unit for discharging the second exhaust gas; and a hot air generating furnace for generating the third exhaust gas, wherein the control means mixes the second exhaust gas and the third exhaust gas. Produce mixed gas, this mixed gas And introducing into said crushed wood drying apparatus, as the drying air flow.

  Further, the wood powder fuel combustion method according to the present invention includes a pulverization and drying step in which wood is pulverized and dried by an air flow for drying to produce wood powder fuel and transported together with the first exhaust gas, and is transported by the first exhaust gas. And collecting the wood powder fuel and discharging a second exhaust gas generated by removing the wood powder fuel from the first exhaust gas, and burning the wood fuel by a boiler A combustion step for discharging the combustion exhaust gas, and controlling the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C. A drying airflow introduction step for preventing condensation, wherein the drying airflow introduction step mixes the second exhaust gas and the combustion exhaust gas to generate a mixed gas, and the mixed gas is used as the drying airflow. To And butterflies.
  In another wood powder fuel combustion method according to the present invention, a pulverization and drying step in which wood is pulverized and dried by an air flow for drying to produce wood powder fuel and transported with the first exhaust gas, and the first exhaust gas is used. A wood powder fuel collecting step of collecting the transported wood powder fuel and discharging a second exhaust gas generated by removing the wood powder fuel from the first exhaust gas; and the wood powder fuel as a boiler And a combustion step of discharging the combustion exhaust gas by the combustion, and sulfur in the first exhaust gas by controlling the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C. A step of introducing an air flow for drying that prevents condensation of components and a step of generating a third exhaust gas, wherein the step of introducing an air flow for drying mixes and mixes the second exhaust gas and the third exhaust gas. Produce gas , And introducing the mixed gas into grinding drying apparatus as the drying air flow.

  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.

As described above, according to the engagement by a tree in powder fuel combustion device and the wood powder fuel combustion method in the present invention, even when the wood powder as fuel, ignition of a mill of sulfur dew formation and wood It is possible to pulverize and dry the wood powder sufficiently finely while preventing the above.

  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. A characteristic point in the present embodiment is that the low oxygen concentration (inert gas having an oxygen concentration of 2 to 5%) discharged from the ECO 14 ′ (Economizer: economizer) provided at the outlet of the boiler 14 in the mill 11. ) 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.

  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.

  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 airflow 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.

  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.

  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.

1 shows an overall configuration of a pulverized fuel combustion apparatus according to a first embodiment of the present invention. The modification of 1st Embodiment is shown. The whole structure of the pulverized fuel combustion apparatus which concerns on the 2nd Embodiment of this invention is shown. The whole structure of the pulverized fuel combustion apparatus which concerns on a prior art is shown. The whole structure of the pulverized fuel combustion apparatus which concerns on a prior art is shown.

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 ... Desulfurizer, 19 ... Chimney, 20 ... Blower, 21 ... Conveying pipe, 22 ... Hot air generator, 23 ... Cyclone, 30 ..Control unit 31 ... Temperature sensor.

Claims (5)

A wood crushing and drying device for crushing wood and drying it with an air flow for drying to produce wood powder fuel and discharging it together with the first exhaust gas;
A boiler that emits combustion exhaust gas by burning the wood powder fuel as a fuel;
Control means for controlling the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C .;
The wood powder fuel transported by the first exhaust gas from the wood grinding and drying device is collected between the wood grinding and drying device and the boiler, and the wood powder fuel is removed from the first exhaust gas. A wood powder fuel collector for discharging the generated second exhaust gas,
The drying air flow, the second exhaust gas is mixed with the combustion exhaust gas to produce a mixed gas, you characterized by introducing the mixture gas into the crushed wood drying apparatus, as the drying air flow Wood powder fuel combustion device. A wood crushing and drying device for crushing wood and drying it with an air flow for drying to produce wood powder fuel and discharging it together with the first exhaust gas;
A boiler that emits combustion exhaust gas by burning the wood powder fuel as a fuel;
Control means for controlling the temperature of the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C .;
The wood powder fuel transported by the first exhaust gas from the wood grinding and drying device is collected between the wood grinding and drying device and the boiler, and the wood powder fuel is removed from the first exhaust gas. A wood powder fuel collector for discharging the generated second exhaust gas;
And a hot air generator furnace for generating a third exhaust gas,
Wherein, the second in exhaust gas is mixed with the third exhaust gas to generate a mixed gas, you characterized by introducing the mixture gas into the crushed wood drying apparatus, as the drying air flow Wood powder fuel combustion device. The wood powder fuel combustion apparatus according to claim 1 or 2 , further comprising a wood powder fuel storage unit that stores the wood powder fuel collected by the wood powder fuel collection unit. A crushing and drying step of crushing wood and drying it with an air stream for drying to produce wood flour fuel and transport it together with the first exhaust gas;
A step of collecting the wood powder fuel transported by the first exhaust gas and discharging a second exhaust gas generated by removing the wood powder fuel from the first exhaust gas;
A combustion step of burning the wood powder fuel by a boiler and discharging combustion exhaust gas;
A drying air flow introducing step for controlling the temperature of the first exhaust gas to prevent condensation of sulfur components in the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C. ,
The drying airflow introducing step, the second said exhaust gas by mixing the combustion exhaust gas to generate a mixed gas, wood flour fuel combustion method you characterized by the mixed gas and the drying gas stream . A crushing and drying step of crushing wood and drying it with an air stream for drying to produce wood flour fuel and transport it together with the first exhaust gas;
A step of collecting the wood powder fuel transported by the first exhaust gas and discharging a second exhaust gas generated by removing the wood powder fuel from the first exhaust gas;
A combustion step of burning the wood powder fuel by a boiler and discharging combustion exhaust gas;
An air flow introduction step for drying that controls the temperature of the first exhaust gas to prevent condensation of sulfur components in the first exhaust gas so that the temperature of the first exhaust gas becomes 110 ° C. to 130 ° C .;
And a step of generating a third exhaust gas,
The drying air flow introducing step is characterized in that the second exhaust gas and the third exhaust gas are mixed to generate a mixed gas, and the mixed gas is introduced into the pulverization drying apparatus as the drying air flow. Wood powder fuel combustion method.

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