JP4353391B2 - Solid fuel combustion burner, combustion method and combustion apparatus using the burner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid fuel combustion burner that can cope with a wide range of furnace load changes even when low-grade coal having an ash content of 20% or more and a moisture content of 30% or more is used as a fuel, and a combustion method and a combustion apparatus using the burner.
[0002]
[Prior art]
In the overseas electric power market, where the demand for energy is expected to increase at present, the use of low-grade coals such as lignite and lignite, which have a high water content and ash content and low calorific value, will be the main factor. Among low-grade coals, lignite has a large reserve, but compared to bituminous coal, it is difficult to cause stable combustion using a burner, such as a decrease in flame temperature and deterioration in combustibility. Brown coal is a coal used as a fuel for thermal power plants mainly in Eastern Europe, and is generally a young coal with an ash content of 20% or more and a water content of 30% or more. Until now, only high-quality bituminous coal has been imported and used in Japan, so there is almost no technology related to lignite combustion. However, domestic power demand is expected to remain sluggish in the future, and in order to expand into overseas markets, it is essential to establish low-grade coal combustion technology centered on lignite.
[0003]
First, the idea about the combustion of general brown coal etc. is shown. Brown coal or the like is an inexpensive fuel, but has problems in its combustibility and ash adhesion due to its properties of high ash, high moisture, and low calorific value. As for its combustibility, how to promote ignition and form a stable flame is the key technology for high-efficiency combustion. Moreover, the reason why the ash adherence to the burner structure and the furnace wall surface is high is that the low melting point is also a disadvantageous property such as lignite. In addition to problems with ash properties such as high contents of calcium, sodium, etc., brown coal etc. are supplied to the furnace in large quantities (the calorific value is less than bituminous coal, so it is necessary to increase the amount of coal input) It is also a coal with unfavorable conditions for slagging and fouling such as a large amount of ash generation. Therefore, in order to use low-grade coal such as lignite and lignite in the burner, it is necessary to achieve both high efficiency combustibility and reduced ash adhesion.
[0004]
Common brown coal burning methods used overseas are the tangential firing method and the corner firing method. The former is a system in which a burner compartment consisting of a fuel flow path and a combustion air flow path is installed on the furnace side wall, and the latter is a system in which a burner compartment consisting of a fuel flow path and a combustion air flow path is installed at the four corners of the furnace. .
[0005]
These combustion methods are different from the so-called opposed combustion method in which the burner groups are arranged so as to be paired with opposing furnace wall surfaces often used in domestic bituminous coal combustion.
The opposed combustion method operates each burner (multiple tube of fuel and combustion air) in a self-flame holding method, whereas the lignite combustion method does not self-flame in the vicinity of the burner outlet but is used for combustion. This is a system in which the air jet has a momentum and is stably burned by mixing and burning at or near the center of the furnace.
[0006]
9 and 10 are front views of an example of the burner compartment 22 in the tangential firing method and the corner firing method, respectively, as viewed from the furnace side. The flow rate of combustion air varies depending on its role. For example, the central air 24 is rapidly mixed with the fuel 25 from the fuel flow path 25 ′ supplied with exhaust gas, and the purpose is to promote combustion by increasing the oxygen concentration. The outermost air 26 is a jet having a penetrating force of 50 m / s or more, and aims to stabilize the combustion from the center of the furnace to the vicinity thereof. As shown in FIG. 9, the burner compartment 22 is composed of only fuel and combustion air. However, as shown in FIG. 10, the burner compartment 22 is provided with a starting oil burner 27 and an auxiliary combustion oil burner 28.
[0007]
[Problems to be solved by the invention]
In the field of burning low-grade coal, mainly lignite, which has little experience in the past, a technology that is indispensable in order to have an advantage in overseas markets is load handling operation technology that responds to fluctuations in demand for electricity. In Eastern Europe, it is sometimes desirable to operate a boiler with a partial load of 30% of the power demand. On the other hand, the prior art has the following problems.
[0008]
As mentioned earlier, what is important in the conventional technology related to lignite combustion (tangential firing method or corner firing method) is that the jet of mixed fluid of fuel and combustion air has a penetrating force to stabilize in the furnace. To burn. Since the gradually lowering the load of the furnace momentum of the jet from the burner compartment 22 is reduced, the flame becomes unstable. FIG. 11 is a horizontal sectional view of the inside of the furnace 11 showing an example of a change in flame shape when the load of the furnace 11 in the corner firing system is lowered from a high load to a low load. When the load is high as shown in FIG. 11A, the jet from the burner compartment 22 forms a blow-off portion 29 near the base of the burner, forms a stable combustion region from the center of the furnace 11 to the vicinity thereof, and efficient combustion is achieved. Done.
[0009]
However, when the load is low, the flow velocity of each jet from the burner compartment 22 decreases and the momentum decreases, so the stable combustion region shown in FIG. 11A is not formed, and the combustion becomes unstable (FIG. 11B). ) The entire furnace 11 becomes dim as shown in FIG. As a measure of whether a stable combustion region is formed in the furnace 11 for safety measures for preventing misfire at low load, as shown in the sectional view of the furnace 11 in FIGS. 12 (a) and 12 (b). Although the flame detector 30 is installed on the top of the furnace 11, when the brightness in the furnace 11 decreases as shown in FIG.
[0010]
For these reasons, it is difficult to operate at low load in the conventional method in which the formation of a stable combustion region in the furnace depends on the momentum from each jet. 12 (a) and 12 (b), a burner compartment 22 is provided in the lower part of the furnace 11, and a jet of mixed fluid of fuel and combustion air from the burner compartment 22 is used for combustion from the after air port 47. A flame is formed by supplying air.
[0011]
An object of the present invention is a furnace using a solid fuel combustion burner of a tangential fire and a corner fire method in which it is difficult to reduce the load even with a burner using low-grade coal such as lignite and lignite. It is to provide a combustion technology for low-grade coal such as lignite that enables stable combustion in both low-load regions and can cope with a wide range of furnace load changes.
[0012]
[Means for Solving the Problems]
The above-described problems of the present invention are solved by the following configuration.
(1) A central air nozzle that ejects air, a solid fuel disposed outside the central air nozzle and a fuel nozzle that ejects the carrier gas, and one or more combustion airs disposed outside the fuel nozzle One or more single burners each having a swirler capable of swirling fluid flowing in the central air nozzle and the one or more outer air nozzles. When, further to the outside than the outer air nozzle of each single burner, a solid fuel combustion burner having the outermost air nozzle disposed at an interval containing the occlusion.
Further, the outermost air nozzles arranged at intervals further including the closed portion outside the outer air nozzles of the single burners are arranged above and below the outer air nozzles of the one or more single burners. Can be done.
Further, a guide that allows a part of the combustion air ejected from the nozzle to flow along the wall surface on which the burner is installed can be provided at the outer air nozzle outlet disposed on the outermost side of the solid fuel combustion burner.
[0013]
(2) A combustion method using the burner for solid fuel combustion as described in (1) above, wherein at the time of low load, the swirler of the outer air nozzle is operated to swirl the outer air, and in the high load region A combustion method using a solid fuel combustion burner that ejects the outer air without swirling without operating the swirler.
[0014]
(3) A combustion method using the burner for solid fuel combustion as described in (1) above, wherein at the time of low load, the swirler of the center air nozzle is operated to swirl the center air, and in the high load region A combustion method using a solid fuel combustion burner that ejects without turning a central air without operating a swirler.
[0015]
(4) The solid fuel combustion burner described in (1) above is used as a unit, and a plurality of the burners are arranged in pairs at four corners (corner firing method) or opposite side wall surfaces (tangential firing method). Combustion device (furnace).
[0016]
(5) A method of operating a combustion apparatus using the combustion apparatus described in (4) above, in which the fuel jet is not ignited from the base of the burner (hereinafter this state is referred to as “blow-off”) in a high load region It is operated by a combustion method in which it is mixed from the center of the device to the vicinity to form a flame, and in a low load range, a fuel jet is ignited from the base of the burner and individual flames are formed at the fuel jet outlet (hereinafter referred to as “self” The operation method of the combustion apparatus operated by the "flame holding system".
[0017]
As a method of distinguishing between the high load region and the low load region, when reducing the load, the flame in the center of the combustion device is visually detected and detected by a flame detector installed at the top of the combustion device, and the region where the combustion device load is higher than the detection limit. A high load region can be set, and a region where the combustion apparatus load is lower than the detection limit can be set as a low load region.
[0018]
In addition, burner combustion air flow distribution has the highest flow rate of combustion air ejected from the outermost air nozzle in the high load range and the highest flow rate of combustion air ejected from the outer air nozzle in the low load range. It is desirable to do.
[0019]
[Action]
The present invention is a conventional tangential firing or corner firing combustion type burner that is difficult to operate at a low load of the furnace, and in a high load region, a stable flame combustion region from the center of the furnace to the vicinity thereof. The system is operated by the forming method, and is operated by the self-flame holding type system in the low load range. By using the combustion method, even furnaces using low-grade coal such as lignite and lignite as fuel can cope with a wide range of furnace load changes (specifically, 30% to 100%) according to power demand.
[0020]
Specifically, the burner is formed at the base of the fuel jet of the burner in the high load region, and burned from the base of the fuel jet of the burner in the low load region to operate the burner as a self-flame holding type. Adjust the air flow distribution of the combustion air (outer air and outermost air) of the burner used, and / or adjust the swirl force of the combustion air using a swirler provided on the outer air nozzle of the burner. Thus, the blow-off or ignition of the fuel jet base of the burner is controlled.
[0021]
According to the present invention, since operation corresponding to electric power demand can be performed, the boiler furnace does not generate power steam more than necessary, can be operated efficiently, and the cost of burner operation can be greatly reduced.
[0022]
Also, in the low load area of the furnace, since the base of the burner fuel jet is ignited, there is a concern that ash will adhere to the wall surface of the burner jet outlet, but the combustion air flows along the furnace wall surface to the outer air nozzle. By providing the guide at the outlet of the outer air nozzle so as to flow, it is possible to prevent ash from adhering to the furnace wall surface and the burner tip near the burner jet root.
[0023]
In order to monitor the combustion state of the fuel in the furnace, the combustion state in the furnace is monitored by a flame detector installed at the top of the furnace during high-load operation, and installed at a furnace position that is almost the same height as the fuel jet during low-load operation. By using the flame detector to monitor the flame at the base of each fuel jet, the load can be changed significantly compared to the conventional method that only monitors the center of the furnace, and safe operation is possible. become.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 4 shows a configuration of a general lignite-fired boiler furnace 11. FIG. 4A is a side view of the tangential firing type lignite-fired boiler furnace 11, and FIG. 4B is a horizontal sectional view of the furnace 11 of FIG. 4A.
[0025]
In the lignite-fired boiler, the combustion gas (about 1000 ° C.) is normally drawn from the furnace 11 from the upper part of the furnace 11 using the exhaust gas duct 32, and the lignite supplied from the coal bunker 34 is simultaneously dried and pulverized by the fan mill 33. A heat transfer tube 35 is disposed in the upper part of the furnace 11. In the corner-fired and tangential-fired burners, one fan mill 33 is installed for each burner compartment 22 (see FIGS. 9 and 10).
[0026]
FIG. 1 is a horizontal sectional view of a furnace 11 provided with a corner firing type burner according to a first embodiment of the present invention.
In the corner firing type burner, a horizontal portion for installing the burner compartment 22 is usually provided at the four corners of the furnace 11. When a high load is applied to the furnace 11 shown in FIG. 1A, jets from the burners of the burner compartment 22 form a blow-off portion 29 at the root of the burner, thereby forming a stable combustion region in the furnace 11.
[0027]
As an example of the operation of the corner firing type burner shown in FIG. 1, for example, the flow velocity of the outermost air 26 (see FIGS. 6 and 7) that contributes to the formation of a stable combustion region in the furnace is 50 m / s or more, The flow rate of the fuel 25 supplied as exhaust gas is 5 m / s to 30 m / s, and the flow rate of the central air 24 that promotes ignition of the fuel is 5 m / s to 20 m / s. When the furnace 11 shown in FIG. 1B is under a low load condition, the distribution and swirling of combustion air are changed later to form a self-flame holding flame 36 (see FIGS. 6 and 7) from each burner. . FIG. 2 shows an embodiment in which fuel is supplied into the furnace 11 from four burner compartments 22 provided on each side wall of the furnace 11, and FIG. 3 shows six burner compartments 22 provided on each side wall of the furnace 11. This is an embodiment in which fuel is introduced into the furnace 11.
[0028]
FIG. 5 shows a modification example of the burner compartment 22 for self-holding the flame when the furnace 11 is operated at a low load. FIG. 5 (b) shows an existing burner compartment 22, and FIG. 5 (a) shows a concentric arrangement of a fuel nozzle and a plurality of combustion air nozzles without modifying the water wall provided on the wall surface of the furnace 11. The front view seen from the furnace 11 inside of the compartment 22 remodeled to the arrange | positioned multiple tube structure is shown. The modified compartment 22 is composed of a burner 37 having a multi-tube structure and a flow path 26 'containing only combustion air (outermost air 26). In the burner 37, the flow path 24 'for the central air 24, the flow path 25' for the fuel 25, and the outer air flow path (the flow path 38 'for the secondary outer air 38, the flow path 39' for the tertiary outer air 39) are concentric. It is configured. The center air 24 is supplied into the fuel flow path 25 in order to increase the oxygen concentration so that the fuel composed of low-grade coal such as lignite conveyed by exhaust gas is easily ignited. The air (secondary outer air 38 and tertiary outer air 39) supplied to the outer air flow paths 38 'and 39' is for forming a self-flame retaining flame 36 (see FIGS. 6 and 7). is there. The ash adhesion prevention guide 40 will be described later.
[0029]
FIG. 6 is a detailed sectional view of a part of the burner compartment 22 after modification shown in FIG. 4 (a), and shows an operation example when the furnace 11 is under a low load. When the furnace 11 is operated at a low load, most of the combustion air is supplied from the burner 37 into the furnace 11 and used as the seal air 41. At this time, the flow rate of the outermost air 26 introduced from the outside of the burner 37 is a slight amount (flow velocity: ˜3 m / s). The flow rate distribution of the combustion air is defined as outer air (secondary outer air 38 + tertiary outer air 39)> center air 24 >> sealing air 41, outermost air 26.
[0030]
A swirler 42 is provided in the central air flow path 24 ′, and the central air is swirled to improve mixing with pulverized coal fuel such as lignite conveyed by exhaust gas, to increase the oxygen concentration, and to ignite easily. To do. The flow paths 38 ′ and 39 ′ of the secondary outer air 38 and the tertiary outer air 39 are provided with vanes 45 and 46, respectively, and the secondary outer air 38 and the tertiary outer air are provided by the vanes 45 and 46 during low load operation of the furnace 11. By setting the turning of 39 to be strong and circulating the high temperature gas to the base of the burner 37, a self-flame holding type flame 36 that holds the flame from the base of the burner 37 is formed. The most concern with the self-flame holding flame 36 is that ash adheres to the wall surface of the furnace 11 near the burner 37 when the flame approaches the root of the burner. For this, an ash adhesion preventing guide 40 that allows the outermost air 26 to flow along the closed portion 43 corresponding to the furnace wall surface is installed at the outlet of the tertiary outer air flow path 39 ′, thereby By flowing the part as seal air 41 on the surface of the blocking part 43, it is possible to prevent ash from adhering to the blocking part 43.
[0031]
FIG. 7 shows an operation example of the furnace 11 when the load is high. During high-load operation of the furnace 11, most of the combustion air is distributed to the central air 24 inside the burner 37 and the outermost air 26 outside the burner. In order to form the flame blow-off portion 29, the flow rates of the secondary outer air 38 and the tertiary outer air 39 are set to a slight amount in order to prevent the hot gas from rewinding to the base of the burner 37, and the swirl is not applied. Further, it is desirable that the flow rate of the central air 24 is reduced to about 80% or less as compared with a low load.
[0032]
With the above settings, since the oxygen concentration is low at the base of the burner 37 and there is no heat source such as circulation of high-temperature gas, the fuel does not ignite and the blow-off portion 29 is formed. In the center of the furnace 11, stable combustion is performed only by mixing with the jet and outermost air 26 from the other burners 37 to form a stable combustion region. The role of the outermost air 26 in operation at a high load is to stabilize the formation of the combustion region in the furnace as in the conventional case. For example, the flow rate is preferably 50 m / s or more.
[0033]
That is, according to the present invention, in the conventional corner firing and tangential firing type furnace 11, the blow-off portion 29 is formed at the base of the burner 37 of the fuel jet at the time of high load, and a stable combustion region is formed in the furnace 11. By using a self-flame holding method that holds the flame from the root of the fuel jet burner 37 at low load, it is possible to cope with load changes up to a wide load change of the furnace 11.
[0034]
As a specific method, without modifying the water wall structure of each furnace wall surface, a part of the burner compartment 22 is remodeled into a burner structure including fuel and a plurality of combustion air flow paths, and distribution of each combustion air, fuel The operation of the furnace at low and high loads is controlled by the presence or absence of swirling of the jet of combustion air.
[0035]
Further, here, only the method of remodeling a part of the burner compartment 22 without remodeling the water wall is shown, but in the case where a water wall structure is provided between two adjacent burners 37 in a newly installed boiler. The present invention is also applicable. In this case, the blocking portion 43 shown in FIGS. 5 and 6 has a water wall structure. Even when a water wall structure is provided between two adjacent burners 37, it is necessary to separately provide a flow path 26 'for the outermost air 26. In the embodiment of the present invention, the shape of the cross-sectional area of the outermost air 26 is square, but the shape of the cross-sectional area is not limited and may be circular or elliptical.
[0036]
Also, according to the present invention, the burner of the present invention changes the combustion system according to the load of the furnace (a system that forms a stable combustion region from the center of the furnace to its vicinity at high loads, and a self-flame holding flame at low loads. A method for monitoring the flame is important in order to safely operate the furnace 11 in this method. Conventionally, since only the center of the furnace was monitored by the flame detector 30 as shown in FIG. 12, it was installed in the upper part of the furnace 11, but in the operation method shown in the embodiment of the present invention, Since the combustion method varies depending on the load, it is necessary to install a flame detector 31 for monitoring individual flames at the same height as the burner as shown in FIG. By monitoring the center of the furnace when the load is high and the individual flames when the load is low, the burner shown in FIG. 8 can be operated safely.
[0037]
【The invention's effect】
The effects obtained by the present invention are summarized as follows.
(1) Even with a burner that uses low-grade coal, the boiler furnace can be operated with a load according to the power demand, so it is possible to prevent wasteful power generation and significantly reduce costs. (2) The burner base where the fuel jet spouts. Even when the fuel is burned from the ash, ash adhesion to the furnace wall surface can be prevented by flowing the seal air along the boiler furnace wall surface.
[0038]
(3) When the furnace is under high load, the stable combustion area in the center of the furnace is monitored by the flame detector installed at the top of the furnace. When the furnace is under low load, each fuel is detected by the flame detector installed at the same height as the fuel jet. By monitoring the flame at the base of the burner from which the jet flows, it is possible to cope with a wide range of load operations and provide safe operation compared to the monitoring method that has been performed only by the former method.
(4) A burner compartment of either tangential fire or corner fire can be used.
[Brief description of the drawings]
FIG. 1 is a horizontal cross-sectional view of a furnace showing a formation state of a flame by a burner (corner firing method) arrangement in a furnace according to a first embodiment of the present invention (FIG. FIG. 1B shows a low load.
FIG. 2 is a horizontal sectional view of a furnace showing a flame formation state by a burner (tangential fire method) arrangement in a furnace according to a second embodiment of the present invention (FIG. 2 (a) is a high load) FIG. 2 (b) shows a low load.
FIG. 3 is a horizontal cross-sectional view of a furnace showing a flame formation state by a burner (tangential firing method) arrangement in a furnace according to a third embodiment of the present invention (FIG. 3 (a) is a high load) FIG. 3 (b) shows a low load.
FIG. 4 is a configuration diagram of a general lignite-fired boiler (FIG. 4 (a) is a side view and FIG. 4 (b) is a horizontal sectional view of a furnace).
FIG. 5 is a front view of a burner compartment for self-flame holding under low load as viewed from the furnace side (FIG. 5 (a) is an embodiment of the present invention, and FIG. 5 (b) is a conventional example).
6 is a partial detailed view of a burner cross section showing an operation example of the self-flame holding burner of FIG.
FIG. 7 is a partial detail view of a burner cross section showing an operation example of the self-flame holding burner of FIG.
FIG. 8 is a vertical cross-sectional view of a furnace showing an arrangement position of a flame detector in the present invention.
FIG. 9 is a front view showing an example of a burner compartment in the prior art as seen from the furnace side.
FIG. 10 is a front view showing an example of a burner compartment in the prior art as seen from the furnace side.
FIG. 11 is a horizontal cross-sectional view of a furnace showing a change in a combustion region in the furnace at the time of load reduction in a burner corner firing combustion method (FIG. 11 (a) is at a high load and FIG. 11 (b) is a low load). Time).
FIG. 12 is a vertical cross-sectional view of a furnace showing an arrangement position of an in-furnace flame detector for monitoring the center of the furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Boiler furnace 22 Burner compartment 24 Central air 24 'Central air flow path 25 Fuel 25' Fuel flow path 26 Outermost air 26 'Outermost air flow path 29 Blowing part 32 Exhaust gas duct 33 Fan mill 30, 31 Flame detector 34 Coal Bunker 35 Heat transfer tube 36 Self flame holding flame 37 Burner 38 Secondary outer air 38 'Secondary outer air flow path 39 Tertiary outer air 39' Tertiary outer air flow path 40 Ash adhesion prevention guide 41 Seal air 42 Swirler 43 Blocking part 45, 46 Vane

Claims (10)

A central air nozzle that ejects air;
A fuel nozzle that ejects a mixed fluid of solid fuel and its carrier gas disposed outside the central air nozzle;
One or more outer air nozzles for injecting combustion air disposed outside the fuel nozzle;
The central air nozzle and the one or more outer air nozzles each have one or more single burners each having a swirler capable of swirling fluid flowing through the nozzle;
Further outward than the outer air nozzle of each single burner, solid fuel combustion burner comprising the outermost air nozzle disposed at an interval containing the occlusion. Outermost air nozzles that are spaced apart from the outer air nozzles of each single burner and that include a closed portion are disposed above and below the outer air nozzles of the one or more single burners. The burner for solid fuel combustion according to claim 1, wherein: The solid fuel combustion burner according to claim 1, wherein a guide is provided in the interval including the closed portion to flow a part of the combustion gas along the surface of the closed portion as seal air.  2. A combustion method using the burner for solid fuel combustion according to claim 1, wherein a swirler of an outer air nozzle is operated at low load to swirl the outer air, and the swirler is operated at a high load region. A combustion method using a burner for burning a solid fuel, characterized in that the outside air is blown out without swirling.  2. A combustion method using the burner for solid fuel combustion according to claim 1, wherein a swirler of a central air nozzle is operated to swirl the center air at low load, and the swirler is operated at a high load range. A combustion method using a burner for solid fuel combustion, characterized in that the air is ejected without swirling the central air. A combustion apparatus comprising a furnace in which the solid fuel combustion burner according to claim 2 is used as a unit, and the plurality of units are arranged in pairs at four corners or opposite side walls of the furnace . Flame detectors for detecting the flame formed in the combustion device are placed above the furnace wall above the wall where the solid fuel combustion burner is installed, and near the wall where the solid fuel combustion burner is installed. The combustion apparatus according to claim 6 . A method of operating a combustion apparatus using the combustion apparatus according to claim 6, wherein in a high load region, a fuel jet is not ignited from the root of the burner but is mixed at the center of the combustion apparatus to form a flame and burn it A method of operating a combustion apparatus, wherein the fuel jet is ignited from the root of the burner at a low load region, and the individual flames are formed at the fuel jet outlet. A method of operating a combustion apparatus using the combustion apparatus according to claim 6, wherein a flame in the center of the combustion apparatus is visually observed and installed in the upper part of the combustion apparatus at the time of load reduction as a method for distinguishing between a high load area and a low load area. A method for operating a combustion apparatus, characterized by detecting with a detector, and setting an area where the combustion apparatus load is higher than the detection limit as a high load area and an area where the combustion apparatus load is lower than the detection limit as a low load area. For burner combustion air flow distribution, operation is performed with the highest flow rate of combustion air ejected from the outermost air nozzle in the high load range and the highest flow rate of combustion air ejected from the outer air nozzle in the low load range. The operation method of the combustion apparatus according to claim 8 .

Images