JP5800423B2 - Burner and boiler equipped with it - Google Patents

Description

  The present invention relates to a burner that can be used, for example, in a pulverized coal-fired boiler that can reduce the amount of slagging on the wall of a boiler furnace, and a boiler equipped with the burner.

Generally, coal fuel has a larger amount of carbon in the fuel than oil and gas fuel, and the amount of carbon dioxide generated increases when used as boiler fuel. However, since coal has a large amount of resources, it must be used effectively.
One method for recovering carbon dioxide from coal-fired boiler exhaust gas (and then storing and sequestering it in the ground and in the sea) is oxygen / carbon dioxide combustion. Oxygen / carbon dioxide combustion is a system in which pulverized coal is burned with oxygen separated from air, and since nitrogen is hardly contained in the exhaust gas, carbon dioxide separation from the exhaust gas is unnecessary.

  Specifically, as shown in FIG. 5, a boiler plant that performs oxygen / carbon dioxide combustion includes a pulverized coal-fired boiler 101, a denitration facility 108, an air heater facility 109, a dust removal facility 110, and a desulfurization facility. Equipment 111. On the upstream side of the pulverized coal-fired boiler 101, there are an air separation device 112 that separates the air 104 into oxygen 103 and nitrogen 105, and a pulverized coal machine 106 that pulverizes the coal to a predetermined particle size to make the pulverized coal 107. Is provided. The flue gas exhausted from the pulverized coal-fired boiler 101 passes through the denitration facility 108, the air heater facility 109, the dust removal facility 110, and the desulfurization facility 111, and then partly passes through the exhaust gas recirculation passage 102 to separate the air. It is mixed with oxygen 103 led from the device 112. The oxygen 103 diluted with the recirculated exhaust gas is used as an oxidant for combustion in the pulverized coal burning boiler 101, and burns the pulverized coal 107 supplied from the pulverized coal machine 106.

  FIG. 6 shows a burner provided at each corner of the boiler furnace. Each burner is provided with the pulverized coal nozzle 120 for supplying the pulverized coal described above. From the periphery of the pulverized coal nozzle 120, the mixture of the recirculated gas and the oxygen 103 introduced from the exhaust gas recirculation flow path 102 is provided. It is led into the boiler furnace. As shown in the figure, the oxygen 103 is introduced into the exhaust gas recirculation flow path 102 at an upstream position before branching to each burner. Therefore, since the air-fuel mixture as the oxidant supplied from each burner is guided into the boiler furnace after passing through a sufficient mixing distance, it is introduced with a substantially equal concentration distribution around the pulverized coal nozzle 120. Become.

  On the other hand, when coal with high slagging properties (low ash melting point / high adhesion) is burned using a conventional pulverized coal burner, the molten ash tends to adhere to each part of the furnace wall surface in the boiler. Further, when the amount of ash deposited on the inner wall surface of the boiler furnace increases and slagging grows, there are problems such as heat transfer inhibition of the boiler and damage to the bottom of the boiler furnace due to the fall of a large clinker.

  Moreover, the slagging trouble described above is caused by the fact that the melting temperature of ash is lowered near the inner wall surface of the furnace, and the ash is likely to melt. The following patent documents 1 and 2 are disclosed as a reference for such measures.

  In Patent Document 1, the cost required for remodeling when a coal boiler operated as an existing air combustion boiler is operated as an oxyfuel boiler can be suppressed, and deterioration and slagging of the oxyfuel boiler due to high-temperature gas can be prevented. A highly reliable oxyfuel boiler that can be operated stably over a long period of time is shown.

  Patent Document 2 discloses that a slagging trouble in a coal-fired boiler is prevented, and an unburned content in ash is reduced to improve plant efficiency.

JP 2010-101588 A JP-A-8-152106

  Patent Document 1 describes a method of measuring an oxygen concentration and adjusting an oxygen supply amount supplied to a boiler based on the detected oxygen concentration. However, since a sensor or a control device for measuring the oxygen concentration is used, there is a problem that the configuration of the boiler is complicated.

  In Patent Document 2, pulverized coal and primary air for combustion are injected into a pre-combustion chamber for combustion, secondary air for combustion having a higher oxygen concentration is input for combustion at high temperature, and then combustion gas is input to a furnace. Thus, a method for preventing slagging troubles in a furnace is described. However, there is a problem that the configuration becomes complicated because many peripheral devices for a coal-fired boiler must be installed.

  The present invention has been made in view of such circumstances, and in pulverized coal-fired oxygen / carbon dioxide combustion, a burner capable of reducing the amount of slagging to the furnace wall surface near the burner with a simpler structure, and It aims at providing the boiler provided with this.

In order to solve the above problems, the low slagging burner of the present invention employs the following means.
That is, the burner according to the present invention burns pulverized coal and oxygen in a boiler furnace, and uses the exhaust gas generated by the combustion as a circulating gas into the boiler furnace to perform oxygen / carbon dioxide combustion. And an oxygen supply means for making the oxygen concentration in the inner wall adjacent region adjacent to the inner wall of the boiler furnace higher than in the inner wall separated region farther from the inner wall than in the inner wall adjacent region.

By using an oxygen supply means that makes the oxygen concentration in the inner wall adjacent region adjacent to the inner wall of the boiler furnace higher than in the inner wall separated region farther from the inner wall than in the inner wall adjacent region, the oxygen concentration in the inner wall adjacent region is increased and ash The melting temperature for melting can be increased. By raising the melting temperature of the ash, it becomes difficult for the ash to be melted, and even when the ash collides with the inner wall of the boiler furnace, the adhesion of the ash can be reduced.
In addition, as oxygen concentration of an inner wall adjacent area | region, 21% or more and 30% or less are preferable, for example.

  Furthermore, the burner according to the present invention includes a pulverized coal supply nozzle that supplies pulverized coal, and a circulation gas supply nozzle that is provided so as to surround the pulverized coal supply nozzle and that supplies the circulation gas, wherein the oxygen supply The means has an oxygen supply nozzle that mixes oxygen with the circulating gas flowing in the circulating gas supply nozzle, and the oxygen supply nozzle injects oxygen to the inner wall side of the boiler furnace rather than the pulverized coal supply nozzle. It is characterized by that.

  Since the oxygen supply nozzle is provided on the inner wall side of the boiler furnace than the pulverized coal supply nozzle to inject oxygen, it is possible to increase the oxygen concentration between the pulverized coal supply nozzle and the inner wall of the boiler furnace, that is, in the region adjacent to the inner wall. it can. In this way, by changing the inner wall adjacent region from the reducing atmosphere to the oxidizing atmosphere, the melting temperature of the ash can be increased and the melting of the ash can be reduced.

  Furthermore, the burner according to the present invention includes a pulverized coal supply nozzle that supplies pulverized coal, and a circulation gas supply nozzle that is provided so as to surround the pulverized coal supply nozzle and that supplies the circulation gas, wherein the oxygen supply The means has an oxygen supply nozzle for mixing oxygen with the circulating gas flowing in the circulating gas supply nozzle, and the oxygen supply nozzle is provided so as to surround the pulverized coal supply nozzle, and the center of the pulverized coal supply nozzle The shaft is arranged to be offset from the center of the cross section of the oxygen supply nozzle so as to be separated from the inner wall of the boiler furnace.

  The central axis of the pulverized coal supply nozzle is offset from the center of the cross section of the oxygen supply nozzle so as to be separated from the inner wall of the boiler furnace, so that the circulating gas and oxygen having a higher oxygen concentration toward the inner wall of the boiler furnace Can be supplied. In this way, by changing the inner wall adjacent region from the reducing atmosphere to the oxidizing atmosphere, the melting temperature of the ash can be increased and the melting of the ash can be reduced.

  Furthermore, the burner according to the present invention includes a plurality of burners according to any one of claims 1 to 3, and a boiler furnace body in which swirl combustion is performed inside by each of the burners. To do.

  By using the burner described above, it is possible to provide a boiler that can reduce the adhesion of ash to the inner wall of the boiler furnace.

  According to the present invention, the oxygen supply means is used that makes the oxygen concentration in the inner wall adjacent region adjacent to the inner wall of the boiler furnace higher than in the inner wall separated region farther from the inner wall than in the inner wall adjacent region. This raises the oxygen concentration in the inner wall adjacent region and raises the melting temperature at which the ash melts, thereby making it difficult for the ash to melt. Therefore, even when ash collides with the inner wall of the boiler furnace, it is difficult for ash to adhere to the slagging on the inner wall of the boiler furnace.

It is the cross-sectional view which showed the boiler furnace to which the burner which concerns on this invention is applied. It is the longitudinal cross-sectional view which showed schematic structure of the pulverized coal burning boiler of this invention. It is the sectional side view which showed 1st Embodiment of the burner which concerns on this invention. It is the sectional side view which showed 2nd Embodiment of the burner which concerns on this invention. It is the schematic block diagram which showed the conventional pulverized coal burning oxygen / carbon dioxide combustion boiler system. It is the cross-sectional view which showed the boiler furnace to which the conventional pulverized coal burner is applied.

Hereinafter, an embodiment of a low slagging burner (hereinafter simply referred to as “burner”) according to the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 shows a schematic configuration of a pulverized coal burning boiler 1 to which the burner according to the first embodiment of the present invention is applied. The pulverized coal fired boiler 1 is used in a plant that performs oxygen / carbon dioxide combustion as already described with reference to FIG.
In the pulverized coal fired boiler 1, exhaust gas recirculation gas guided from the exhaust gas recirculation flow path is input into the wind box 6, and oxygen 3 is input to each burner. The pulverized coal fired boiler 1 is a boiler that burns pulverized coal 7 (see FIG. 3) obtained by pulverizing coal with a mill (not shown). The pulverized coal fired boiler 1 has a plurality of burners 10 (see FIG. 3) provided so as to penetrate the furnace wall. By these burners 10, pulverized coal 7 is fed together with air and burned in a boiler furnace, thereby heating a furnace wall water pipe, a superheater and a economizer not shown.

FIG. 2 shows a cross-sectional view of the furnace portion of the pulverized coal burning boiler 1 shown in FIG.
As shown in the figure, the pulverized coal burning boiler 1 has a cross-sectional shape that is substantially square. One burner 10 is provided at each corner of the pulverized coal-fired boiler 1, and four burners 10 are provided in this embodiment. Thus, by arranging each burner 10 in a corner, swirl combustion is performed.
The exhaust gas is guided from the exhaust gas recirculation flow path 2 and is supplied to each port 6 a of the wind box 6. The recirculated gas supplied into the wind box 6 is distributed to each burner 10. FIG. 3 shows the recirculation gas 2 a distributed to each burner 10.

As shown in FIG. 3, each burner 10 includes a pulverized coal supply nozzle 8 and an oxygen supply nozzle 9 that are provided coaxially toward the furnace. The pulverized coal supply nozzle 8 and the oxygen supply nozzle 9 are disposed in a circulation gas supply nozzle 12 that guides the recirculation gas 2a into the boiler furnace. That is, the circulating gas supply nozzle 12 is provided so as to surround the pulverized coal supply nozzle 8 and the oxygen supply nozzle 9.
The pulverized coal supply nozzle 8 is disposed along the substantially central axis of the circulating gas supply nozzle 12. The oxygen supply nozzle 9 is disposed substantially in parallel adjacent to the pulverized coal supply nozzle 8, and is disposed closer to the furnace inner wall 4 (see FIG. 2) than the pulverized coal supply nozzle 8.
Thus, by arranging the oxygen supply nozzle 9 closer to the furnace inner wall 4 than the pulverized coal supply nozzle 8, a region having a high oxygen concentration can be formed on the furnace inner wall 4 side. That is, as shown in FIG. 2, the inner wall adjacent region 14, which is the space region between the flame 5 and the furnace inner wall 4, is higher in oxygen than the inner wall separation region that is the space region from the flame 5 to the boiler furnace center side. Concentration. The oxygen concentration in the inner wall adjacent region 14 is preferably in the range of 21% to 30%.

Next, the operation of the burner having the above configuration will be described.
The pulverized coal 7 pulverized by a mill (not shown) passes through the pulverized coal supply nozzle 8 and is guided into the boiler furnace. The pulverized coal introduced into the furnace is ignited to form a flame 5. In order to supplement combustion of the flame 5, recirculation gas is supplied from a recirculation gas supply nozzle surrounding the pulverized coal supply nozzle 8, and oxygen 3 is supplied from an oxygen supply nozzle 9. Since the oxygen supply nozzle 9 is installed closer to the furnace inner wall 4 than the pulverized coal supply nozzle 8, an air-fuel mixture having a high oxygen concentration flows along the furnace inner wall 4 side. Thereby, the air-fuel mixture having a higher oxygen concentration flows in the inner wall adjacent region 14 than in the inner wall separation region.

According to this embodiment, there exist the following effects.
Since oxygen is supplied to the furnace inner wall 4 side of the boiler 1 by the oxygen supply nozzle 9 provided on the furnace inner wall 4 side of the pulverized coal supply nozzle 8, the oxygen concentration is in the inner wall adjacent region 14 near the furnace inner wall 4. A high air-fuel mixture can be supplied. As a result, an oxidizing atmosphere that can increase the melting temperature of the ash as compared with the reducing atmosphere can be formed in the inner wall adjacent region 14, so that the furnace inner wall 4 even when the ash collides with the furnace inner wall 4 of the boiler 1. Ashes can be prevented.
In particular, in the present embodiment, since the oxygen supply nozzles 9 are individually provided for each burner 10, as shown in FIG. 6, the oxygen supply nozzle 9 is provided in the flow path upstream of the wind box connected to the burner. Unlike the case of mixing the oxygen, oxygen can be supplied so that the oxygen concentration distribution at the outlet of each burner 10 becomes a desired distribution. Thereby, since the oxygen concentration of the inner wall adjacent area | region 14 can be adjusted in detail, adhesion of the ash on the furnace inner wall 4 can further be prevented.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the configuration of the oxygen supply nozzle 9 is different from that of the first embodiment, and the others are the same. Therefore, the same reference numerals are assigned to the same components, and the description thereof is omitted.

As shown in FIG. 4, the oxygen supply nozzle 15 is provided so as to surround the pulverized coal supply nozzle 8. The central axis of the pulverized coal supply nozzle 8 is offset from the center of the cross section of the oxygen supply nozzle 15 so as to be separated from the inner wall of the boiler furnace.
Thereby, compared with the case where the center axis | shaft of the pulverized coal supply nozzle 8 is made to correspond with the cross-sectional center of the oxygen supply nozzle 15, the oxygen channel cross-sectional area by the side of the furnace inner wall 4 (refer FIG. 2) increases. Therefore, a large amount of air-fuel mixture having a high oxygen concentration can be supplied along the furnace inner wall 4 of the boiler 1.

  According to the present embodiment, a large amount of air-fuel mixture having a high oxygen concentration is supplied along the furnace inner wall 4 of the boiler 1 so that the inner wall adjacent region in the boiler can be made an oxidizing atmosphere, and the ash is melted. It becomes difficult. Thereby, even when ash collides with the furnace inner wall 4 of the boiler 1, adhesion of ash can be reduced.

1 boiler (pulverized coal fired boiler)
2 Circulating gas 3 Oxygen 4 Furnace inner wall 5 Flame 6 Wind box 7 Pulverized coal 8 Pulverized coal supply nozzle 9 Oxygen supply nozzle 10 Burner 12 Circulating gas supply nozzle 14 Inner wall adjacent area 15 Oxygen supply nozzle

Claims (5)

In a burner used for a boiler that burns pulverized coal and oxygen in a boiler furnace, guides exhaust gas generated by combustion into the boiler furnace as a circulating gas, and performs oxygen / carbon dioxide combustion,
A pulverized coal supply nozzle for supplying pulverized coal;
A circulating gas supply nozzle that is provided so as to surround the pulverized coal supply nozzle and supplies the circulating gas;
An oxygen supply nozzle for mixing oxygen with the circulation gas flowing in the circulation gas supply nozzle,
The oxygen supply nozzle injects oxygen toward the inner wall side of the boiler furnace than the pulverized coal supply nozzle, thereby causing the oxygen concentration in the inner wall adjacent region adjacent to the inner wall of the boiler furnace to be higher than that in the inner wall adjacent region. A burner characterized in that the burner is made higher than an inner wall separation region away from the inner wall. In a burner used for a boiler that burns pulverized coal and oxygen in a boiler furnace, guides exhaust gas generated by combustion into the boiler furnace as a circulating gas, and performs oxygen / carbon dioxide combustion,
A pulverized coal supply nozzle for supplying pulverized coal;
A circulating gas supply nozzle that is provided so as to surround the pulverized coal supply nozzle and supplies the circulating gas;
An oxygen supply nozzle for mixing oxygen with the circulation gas flowing in the circulation gas supply nozzle,
The oxygen supply nozzle is provided so as to surround the pulverized coal supply nozzle,
The central axis of the pulverized coal supply nozzle is offset from the center of the cross section of the oxygen supply nozzle so as to be separated from the inner wall of the boiler furnace, thereby adjacent to the inner wall of the boiler furnace. The burner according to claim 1, wherein the oxygen concentration of the inner wall is higher than that of the inner wall separation region and the inner wall separation region far from the inner wall. The burner according to claim 1 or 2, wherein the pulverized coal supply nozzle is disposed along a substantially central axis of the circulating gas supply nozzle. The burner according to any one of claims 1 to 3, wherein an oxygen concentration in the inner wall adjacent region is in a range of 21% to 30%. A plurality of burners according to any one of claims 1 to 4 ,
A boiler furnace body in which swirl combustion is performed by each burner;
The boiler characterized by having.

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