JP2006038340A - Combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion device reducing NOx and unburned combustibles included in exhaust gas without causing substantial increase of a facility cost. <P>SOLUTION: In a pulverized coal burning boiler 1 of a composition provided with a furnace body 2, a combustion part 3 carrying out combustion of pulverized coal which is fuel, and a convection heat transfer part 4 recovering heat from combustion gas generated by the combustion part 3, an oxygen supplying device 21 supplying oxygen containing gas into the convection heat transfer part 4 is provided in the convection heat transfer part 4, and an area in the furnace body 2 from a directly above position of a burner 11 of the combustion part 3 to the convection heat transfer part 4 is used as a reduction area D carrying out reduction of the combustion gas. The oxygen supplying device 21 has a discharge part 22 with at least one part inserted in an area subsequent to the reduction area D in the furnace body 2, and a plurality of discharge openings 23 discharging the oxygen containing gas is provided in a portion inserted into the furnace body 2 of the discharge part 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a combustion apparatus such as a coal-fired boiler.

As a combustion apparatus that burns fuel in a furnace and obtains high-temperature combustion gas, for example, there is a combustion apparatus described in Patent Document 1 described later.
The combustion apparatus described in Patent Document 1 uses a multistage combustion method. In the multi-stage combustion method, the air supplied to the burner section for burning the fuel is throttled to suppress the generation of NO _X due to combustion, and the NO _x generated by the combustion is reduced using the combustion gas as a reducing atmosphere. In this method, unburned components in the combustion gas are completely burned by introducing air into the combustion gas.
Thus the environmental impact can be reduced by reducing the amount of the NO _X produced by the combustion, the operating costs by improving the utilization efficiency of the fuel by reducing the unburned in the combustion gas combustion apparatus Can be reduced.
In the multistage combustion method, generally, a method called OFA (Over Fire Air) is used in which air is introduced directly above the burner portion.

JP-A-9-126416 (second page, third page, and FIG. 1)

To reduce NO _X generated by combustion, it is necessary to some residence time of combustion gas in the furnace.
However, the size of the furnace itself is limited due to restrictions on the installation space of the furnace and equipment costs. For this reason, there is a limit to the size of an area for retaining NO _X (hereinafter referred to as a reduction area), and it has been difficult to sufficiently reduce the generated NO _X.
On the other hand, if the reduction area is expanded, the position where the air for complete combustion is introduced moves to the downstream side, so that the residence time of the combustion gas into which the air is introduced becomes shorter and the unburned portion is completely removed. It becomes difficult to burn, and the unburned content in the exhaust gas increases.
Furthermore, when simply put air into the combustion gas, there is a case where intermediate products of ammonia or cyanogen, etc. contained in the combustion gas will be converted to NO _X, the amount of rapidly NO _X is increased .

The present invention was made in view of such circumstances, without causing a significant increase in equipment cost, to provide a reduced NO _X and unburned combustibles in the exhaust gas combustion device With the goal.

In order to solve the above problems, the combustion apparatus of the present invention employs the following means.
That is, the combustion apparatus according to the present invention is a combustion apparatus in which a furnace body is provided with a combustion section in which fuel is burned and a convection heat transfer section that recovers heat from the combustion gas generated in the combustion section. An oxygen supply device that supplies an oxygen-containing gas into the convection heat transfer unit is provided, and a region from the combustion unit to the convection heat transfer unit in the furnace body reduces the combustion gas. It is said that it is said.

In the combustion apparatus configured as described above, the oxygen supply apparatus is configured to supply the oxygen-containing gas into the convection heat transfer section, and the furnace body is configured to reduce the combustion gas from the combustion section to the convection heat transfer section. A reduction region is formed in which is performed.
Thus, in this combustion apparatus, the reduction region is sufficiently secured without increasing the size of the furnace body, so that the combustion gas is sufficiently reduced.
And in the convection heat transfer part, the unburned part in the combustion gas which passed through the reduction | restoration area | region burns by supplying oxygen-containing gas, and the heat | fever generated by this can also be collect | recovered by the convection heat transfer part.

  Further, in this combustion apparatus, the oxygen supply device has a discharge portion into which at least a part is inserted into the furnace body, and a portion of the discharge portion to be inserted into the furnace body includes A plurality of discharge ports for discharging the oxygen-containing gas may be provided.

In the combustion apparatus configured as described above, the oxygen-containing gas is supplied to the convection heat transfer section through the discharge section.
The discharge part is provided with a plurality of discharge ports in the part inserted into the furnace body, oxygen-containing gas is discharged from each discharge port toward the surroundings, and combustion gas and oxygen content are contained in the convection heat transfer unit The gas is quickly mixed.
Thereby, even if the residence time of the combustion gas in the furnace body is short, the unburned content in the combustion gas is burned effectively. That is, an unburned part can be reduced effectively, without enlarging a furnace main body.

Here, the oxygen concentration of the oxygen-containing gas is a concentration at which the combustion gas becomes a reducing atmosphere, and a concentration sufficient to burn the unburned content in the combustion gas (for example, more than 0% and 10% or less). Set to Then, as the oxygen-containing gas, for example, by using a high temperature low oxygen concentration gas of 300 ° C. or higher (preferably 500 ° C. to 800 ° C.), the combustion gas is changed to a high temperature reducing atmosphere, and the combustion gas is reduced. In a state where it is sufficiently performed and the rapid generation of NO _X due to the introduction of oxygen is suppressed, the unburned component contained therein reacts with oxygen and burns, and the unburned component is reduced.

  Further, in this combustion apparatus, the discharge part may be provided with the discharge port that opens in a direction intersecting a direction in which the combustion gas flows in the furnace body.

In the combustion apparatus configured as described above, the discharge portion is provided with a discharge port that opens in a direction intersecting with the direction in which the combustion gas flows, and is separated from the discharge portion in the flow of the combustion gas from the discharge port. Oxygen-containing gas is discharged toward the part.
As a result, the oxygen-containing gas is promptly supplied to each part in the direction intersecting with the flow of the combustion gas (that is, the entire cross section in the oxygen supply part of the flow of the combustion gas). Are uniformly mixed, and combustion of unburned content in the combustion gas is further promoted.

  A combustion apparatus according to the present invention is a combustion apparatus in which a furnace body is provided with a combustion section in which fuel is burned and a convection heat transfer section that recovers heat from the combustion gas generated in the combustion section, The convection heat transfer section is provided at a position lower than the upper end of the combustion section.

In the conventional combustion apparatus, a convection heat transfer unit is connected to the upper end of the combustion unit, and heat is recovered from the combustion gas rising from the combustion unit.
However, the convection heat transfer part has a heat exchanger and the like, and is heavier than the other parts of the furnace body. For this reason, the combustion device requires a large support structure for holding the convection heat transfer section at a high place, and as a result, the entire combustion device is large.
In the combustion apparatus according to the present invention, the heavy convection heat transfer section is provided not at the combustion section but at a lower position, so the support structure for supporting the convection heat transfer section is small. The whole combustion device becomes small.
Further, since the combustion gas descends from the upper end of the combustion section and is supplied to the convection heat transfer section, the combustion gas circulation path is longer than when the convection heat transfer section is connected to the upper end of the combustion section. Therefore, the residence time of the combustion gas becomes long, NO _X and unburned combustibles is reduced.

  A combustion apparatus according to the present invention is a combustion apparatus that obtains combustion gas by burning fuel in a combustion section, and each of the combustion apparatuses has a temperature of 300 ° C. or more from a plurality of locations in the combustion section where the positions of the combustion gas flow differ. It has a high temperature low oxygen concentration gas supply device for supplying a high temperature low oxygen concentration gas.

In the combustion apparatus configured as described above, the combustion gas generated in the combustion section is supplied with a high temperature and low oxygen concentration gas of 300 ° C. or more (preferably 500 ° C. to 800 ° C.) at each section in the flowing direction. Is done. That is, oxygen is added to the combustion gas little by little in the process of flowing downstream.
As a result, the combustion gas is in a high-temperature reducing atmosphere, the combustion gas is sufficiently reduced, and the unburned content contained therein is reduced to oxygen in a state where the rapid generation of NO _X due to the introduction of oxygen is suppressed. It reacts with and burns, and the unburned content is reduced.
Here, the oxygen concentration of the high-temperature low-oxygen concentration gas supplied by the high-temperature low-oxygen concentration gas supply device is a concentration at which the combustion gas becomes a reducing atmosphere and is sufficient to burn the unburned components in the combustion gas. The density is set (for example, more than 0% and 10% or less).

  Further, in this combustion apparatus, the discharge position and / or discharge direction of the high-temperature low-oxygen concentration gas to the combustion section by the high-temperature low-oxygen concentration gas supply device is a position in the combustion section in which the combustion gas flows Each may be different.

  In the combustion apparatus configured as described above, the high temperature and low oxygen concentration gas is supplied to the combustion gas at different positions and / or discharge directions for each position in the flow direction, so that oxygen is uniformly supplied to the entire combustion gas. Can be supplied.

According to the combustion apparatus of the present invention, without causing a significant increase in equipment cost can be reduced NO _X and unburned combustibles in the exhaust gas.

Embodiments according to the present invention will be described below with reference to the drawings.
[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
In this embodiment, an example in which the present invention is applied to a pulverized coal cooking boiler will be described.
The pulverized coal-fired boiler 1 is provided with a combustion unit 3 in which pulverized coal as a fuel is burned and a convection heat transfer unit 4 that recovers heat from the combustion gas generated in the combustion unit 3. It is a combustion device.

  The combustion part 3 has a chimney shape with a substantially square cross section extending in the vertical direction, and the lower region inside thereof is a main combustion region B. In addition, a furnace bottom hopper 3 a for discharging the furnace bottom ash generated by the combustion of pulverized coal to the outside is provided at the bottom of the combustion unit 3.

  A plurality of burners 11 are disposed at the same height of the wall surface 3 b at the lower part of the combustion unit 3 that constitutes the main combustion region B, with their tips directed toward the central axis of the combustion unit 3. . These burners 11 are supplied with pulverized coal together with air from a fuel supply device (not shown), and generate a flame substantially horizontally toward the central axis of the combustion unit 3. In the present embodiment, a plurality of sets of the burners 11 are arranged along the vertical direction.

  An air supply port 12 for supplying air to a position directly above the burner 11 in the combustion unit 3 is provided at a position directly above the burner 11 in the wall surface 3b. Air is supplied to the air supply port 12 from an air supply device (not shown), and an arbitrary amount of air is supplied from the air supply port 12 into the combustion unit 3. That is, the air supply port 12 and the air supply device are configured to perform OFA.

A duct-shaped convection heat transfer section 4 extending in a substantially horizontal direction is connected to the upper end of the combustion section 3.
In the convection heat transfer unit 4, a heat exchanger 16 that recovers the heat of the combustion gas flowing from the combustion unit 3 into the convection heat transfer unit 4 is installed.
The convection heat transfer section 4 is provided with an oxygen supply device 21 that supplies an oxygen-containing gas into the convection heat transfer section 4, and convection transfer is performed from a position directly above the burner 11 of the combustion section 3 in the furnace body 2. A region up to the heat section 4 is a reduction region D that reduces the combustion gas.

  The oxygen supply device 21 has a discharge portion 22 at least partially inserted in a region after the reduction region D in the furnace body 2. A plurality of discharge ports 23 for discharging the oxygen-containing gas are provided in a portion of the discharge unit 22 inserted into the furnace body 2.

In the present embodiment, the oxygen supply device 21 mixes the exhaust gas discharged from the furnace body 2 and the outside air, and has an oxygen concentration of 300 ° C. or higher (preferably within a temperature range of 500 ° C. to 800 ° C.). It has a preparation device 24 for preparing an oxygen-containing gas of more than 0% and 10% or less and supplying it to the discharge unit 22.
Moreover, as the discharge part 22, for example from the ceiling part 4a of the convection heat transfer part 4 to the furnace main body 2 along the direction (namely, substantially vertical direction) substantially orthogonal to the flow of the combustion gas in the convection heat transfer part 4. An inserted pipe is used. As shown in FIG. 2, a plurality of these discharge portions 22 are arranged in parallel in a direction substantially orthogonal to the insertion direction on a virtual plane substantially orthogonal to the flow of combustion gas. In these discharge units 22, all the discharge ports 23 are opened in a direction intersecting with the direction in which the combustion gas flows in the furnace body 2.

In the pulverized coal-fired boiler 1 configured as described above, the combustion unit 3 ignites the burner 11 to generate high-temperature combustion gas, and performs OFA using the air supply port 12 and the air supply device. The combustion gas is adjusted to an appropriate reducing atmosphere within 3.
The combustion gas thus prepared rises in the combustion part 3 by thermal convection, is reduced in the reduction region D, and then sent into the convection heat transfer part 4.
In the convection heat transfer unit 4, the heat of the combustion gas is recovered by the heat exchanger 16, and oxygen is supplied to the combustion gas by the oxygen supply device 21, and unburned components in the combustion gas are burned.

In the pulverized coal-fired boiler 1, a reduction region D where the combustion gas is reduced is formed in the furnace body 2 from the combustion unit 3 to the convection heat transfer unit 4. That is, in this pulverized coal-fired boiler 1, since the reduction region D is sufficiently secured without increasing the size of the furnace body 2, the combustion gas is sufficiently reduced.
And in the convection heat transfer part 4, the unburned part in the combustion gas which passed the reduction | restoration area | region D is combusted by supplying oxygen-containing gas, and the heat | fever generated by this can also be collect | recovered by a convection heat transfer part. it can.

Furthermore, since the oxygen-containing gas supplied to the convection heat transfer unit 4 is a high-temperature, low-oxygen concentration gas of 300 ° C. or higher, the combustion gas is set to a high-temperature reducing atmosphere, and the combustion gas is sufficiently reduced. In addition, while the rapid generation of NO _X due to the introduction of oxygen is suppressed, the unburned component contained therein reacts with oxygen and burns, and the unburned component is reduced.
Moreover, in this pulverized coal cooking boiler 1, the oxygen supply apparatus 21 has the discharge part 22 by which at least one part is inserted in the furnace main body 2, The part inserted in the furnace main body 2 of the discharge part 22 Are provided with a plurality of discharge ports 23 for discharging oxygen-containing gas.
Thereby, oxygen-containing gas is discharged toward the periphery from each discharge port 23 of the discharge part 22, and the combustion gas and oxygen-containing gas are quickly mixed in the convection heat transfer part 4. Even if the residence time of the combustion gas is short, the unburned portion in the combustion gas is burned effectively. That is, the unburned content can be effectively reduced without increasing the size of the furnace body 2.

The discharge port 23 opens in a direction substantially perpendicular to the direction in which the combustion gas flows, and the oxygen-containing gas is discharged from the discharge port 23 toward a portion of the combustion gas flow that is separated from the discharge unit 22. It has come to be.
Thereby, the oxygen-containing gas is promptly supplied to each part in the direction substantially orthogonal to the flow of the combustion gas (that is, the entire cross section in the oxygen supply part of the flow of the combustion gas). Are more uniformly mixed, and combustion of unburned content in the combustion gas is further promoted.

  Here, the supply amount of the high temperature and low oxygen concentration gas by the oxygen supply device 21 is set to an amount sufficient for the combustion gas to be in a reducing atmosphere and to burn the unburned portion in the combustion gas. Further, the flow rate of the oxygen-containing gas discharged from the discharge port 23 is 40 m / second so that the oxygen-containing gas is supplied into the convection heat transfer section 4 at once and mixing of the combustion gas and the oxygen-containing gas is performed quickly. s to 80 m / s, preferably 60 m / s to 80 m / s.

Thus, according to the pulverized coal cooking boiler 1 according to the present embodiment, NO _X and unburned components contained in the exhaust gas can be reduced without causing a significant increase in equipment cost.

  Here, although the example which provided the air supply port 12 for supplying air to the combustion part 3 was shown in this embodiment, it is not restricted to this, The air supply port 12 is omitted and the oxygen supply apparatus 21 is provided. Alternatively, oxygen may be supplied to the combustion gas only.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
The pulverized coal cooking boiler 41 according to the present embodiment is mainly characterized in that, in the pulverized coal cooking boiler 1 shown in the first embodiment, the convection heat transfer unit 4 is provided at a position lower than the upper end of the combustion unit 3. To do. Hereinafter, the same or the same parts as those of the pulverized coal cooking boiler 1 shown in the first embodiment are indicated by the same reference numerals, and detailed description thereof is omitted.

The upper end of the combustion unit 3 and the inlet of the convection heat transfer unit 4 are connected via a chimney-shaped descending flow path 42 extending downward from the side of the upper end of the combustion unit 3.
In the pulverized coal cooking boiler 41, an oxygen supply device 43 is installed in the vicinity of the lower end of the descending flow path 42 instead of installing the oxygen supply device 21 in the convection heat transfer unit 4.
The oxygen supply device 43 discharges the oxygen-containing gas prepared by the preparation device 24 into the furnace body 2 from a discharge port 43a provided in the vicinity of the lower end of the side wall 42a of the descending flow path 42.
In this pulverized coal-fired boiler 41, the reduction region D is installed from the upper end of the main combustion region B of the combustion unit 3 through the upper end of the combustion unit 3 to install the oxygen supply device 21 of the descending flow path 42 and the convection heat transfer unit 4. Up to the position.

In the pulverized coal-fired boiler 41 configured as described above, the heavy convection heat transfer section 4 is provided not at the combustion section 3 but at a lower position, so that the convection heat transfer section 4 is supported. The support structure (not shown) may be small, and the pulverized coal-fired boiler 41 as a whole becomes small.
Further, since the combustion gas is supplied from the upper end of the combustion unit 3 to the convection heat transfer unit 4 via the descending flow path 42, the combustion gas is compared with the case where the convection heat transfer unit 4 is connected to the upper end of the combustion unit 3. The distribution channel is long. Therefore, the residence time of the combustion gas becomes long, NO _X and unburned combustibles is reduced.
In this way, according to the pulverized coal-fired boiler 41, without causing a significant increase in equipment cost can be reduced NO _X and unburned combustibles in the exhaust gas.

  Here, in this pulverized coal-fired boiler 41, instead of installing the oxygen supply device 43, the oxygen supply device 21 may be installed in the vicinity of the lower end of the descending flow path 42 or in the convection heat transfer section 4.

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
The pulverized coal-fired boiler 51 according to the present embodiment is the same as the pulverized coal-fired boiler 1 according to the first embodiment, instead of providing the convection heat transfer unit 4 with the oxygen supply device 21 and supplying the combustion unit 3 with a high-temperature low-oxygen concentration gas. The main feature is that the device 52 is installed.

The high-temperature low-oxygen concentration gas supply device 52 includes the oxygen-containing gas (high-temperature low-oxygen concentration gas) prepared by the preparation device 24 in a plurality of high temperatures provided in a region higher than the main combustion region B of the combustion unit 3. The gas is supplied from the low oxygen concentration gas supply port 53 into the combustion unit 3.
A plurality of these high temperature low oxygen concentration gas supply ports 53 are arranged at the same height of the wall surface 3 b of the combustion unit 3 so as to face the central axis of the combustion unit 3. Further, a plurality of sets of the high temperature low oxygen concentration gas supply ports 53 are arranged in the vertical direction, and the positions around the central axis of the combustion unit 3 are shifted for each set.

  In the present embodiment, the combustion unit 3 is provided with three sets of a first set 53a, a second set 53b, and a third set 53c in order from the lower side as a set of the high temperature low oxygen concentration gas supply ports 53. Yes. Further, as shown in FIG. 5, in the first set 53a and the third set, the high temperature low oxygen concentration gas supply port 53 is provided at the center of each side wall 3b of the combustion unit 3, and in the second set, the combustion is performed. It is provided at each corner of the part 3. Here, in FIG. 5, the flow of the high temperature low oxygen concentration gas discharged from the first group 53a and the third group 53c is shown by a one-dot chain line, and the flow of the high temperature low oxygen concentration gas discharged from the second group 53b is two. It is indicated by a dotted line.

In the pulverized coal-fired boiler 51 configured as described above, the high temperature and low oxygen concentration gas of 300 ° C. or more is supplied to the combustion gas generated in the combustion unit 3 in each part in the flowing direction. That is, oxygen is added to the combustion gas little by little in the process of flowing downstream.
As a result, the combustion gas is in a high-temperature reducing atmosphere, the combustion gas is sufficiently reduced, and the unburned content contained therein is reduced to oxygen in a state where the rapid generation of NO _X due to the introduction of oxygen is suppressed. It reacts with and burns, and the unburned content is reduced.
Here, the oxygen concentration of the high-temperature low-oxygen concentration gas supplied by the high-temperature low-oxygen concentration gas supply device 52 is a concentration at which the combustion gas becomes a reducing atmosphere, and is sufficient to burn unburned components in the combustion gas. (For example, more than 0% and 10% or less).

  Moreover, in this pulverized coal cooking boiler 51, the discharge position and discharge direction of the high-temperature low-oxygen concentration gas to the combustion unit 3 by the high-temperature low-oxygen concentration gas supply device 53 are in each position in the direction in which the combustion gas flows in the combustion unit 3. Therefore, oxygen can be supplied uniformly to the entire combustion gas.

Thus, according to the pulverized coal cooking boiler 51 according to the present embodiment, NO _X and unburned components contained in the exhaust gas can be reduced without causing a significant increase in equipment cost.

It is a longitudinal section showing the composition of the pulverized coal cooking boiler (combustion device) concerning a first embodiment of the present invention. It is AA arrow sectional drawing of FIG. It is a longitudinal cross-sectional view which shows the structure of the pulverized coal cooking boiler concerning 2nd embodiment of this invention. It is a longitudinal cross-sectional view which shows the structure of the pulverized coal cooking boiler concerning 3rd embodiment of this invention. It is CC sectional view taken on the line of FIG.

Explanation of symbols

1,41,51 Pulverized coal-fired boiler (combustion device)
2 Furnace body 3 Combustion unit 4 Convection heat transfer unit 21, 43 Oxygen supply device 22 Discharge unit 23 Discharge port 52 High temperature low oxygen concentration gas supply device D Reduction region

Claims (6)

A combustion apparatus in which a furnace body is provided with a combustion section in which fuel is burned, and a convection heat transfer section that recovers heat from combustion gas generated in the combustion section,
An oxygen supply device for supplying an oxygen-containing gas into the convection heat transfer unit is provided, and a region from the combustion unit to the convection heat transfer unit in the furnace body is a reduction region for reducing the combustion gas. Combustion device characterized by that.   The oxygen supply device has a discharge portion into which at least a part is inserted into the furnace body, and a discharge portion for discharging the oxygen-containing gas is inserted into a portion of the discharge portion that is inserted into the furnace body. The combustion apparatus according to claim 1, wherein a plurality of outlets are provided.   The combustion apparatus according to claim 2, wherein the discharge port is provided with the discharge port that opens in a direction intersecting a direction in which the combustion gas flows in the furnace body. A combustion apparatus in which a furnace body is provided with a combustion section in which fuel is burned, and a convection heat transfer section that recovers heat from combustion gas generated in the combustion section,
The convection heat transfer section is provided at a position lower than the upper end of the combustion section. A combustion device for obtaining combustion gas by burning fuel in a combustion section,
Combustion characterized by having a high-temperature low-oxygen concentration gas supply device for supplying high-temperature low-oxygen concentration gas at 300 ° C. or more from a plurality of locations with different positions in the combustion gas flow direction in the combustion section apparatus.   The discharge position and / or discharge direction of the high-temperature low-oxygen concentration gas to the combustion unit by the high-temperature low-oxygen concentration gas supply device is different for each position of the combustion unit in the direction in which the combustion gas flows. 6. The combustion apparatus according to claim 5, wherein

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