JP3899457B2 - Solid fuel burner and combustion method of solid fuel burner - Google Patents

Description

BACKGROUND OF THE INVENTION
[0001]
The present invention relates to a solid fuel burner that burns by transporting solid fuel in an air flow, and in particular, a solid fuel burner and a solid fuel burner that are suitable for burning fuel with a high water content and volatile content such as pulverized coal, wood, and peat. The combustion method of this invention, the combustion apparatus provided with the solid fuel burner, and the operation method of the combustion apparatus.
[Prior art]
[0002]
Coal, wood, and peat, which have a low degree of coalification such as lignite and lignite, have a large amount of moisture and volatile matter released as a gas when heated. Moreover, compared with coal with high coalification degree, such as bituminous coal and anthracite, calorific value is low, and generally grindability is bad. Furthermore, the melting temperature of combustion ash is low.
[0003]
Since these fuels have a large amount of volatile components, they tend to spontaneously ignite in the air atmosphere during storage and pulverization, and are difficult to handle compared to bituminous coal. In order to prevent spontaneous ignition, when lignite or lignite is pulverized and burned, a mixed gas of combustion exhaust gas and air is used as a fuel carrier gas. Combustion exhaust gas reduces oxygen concentration and prevents spontaneous ignition of fuel. On the other hand, the retained heat of the combustion exhaust gas evaporates moisture in the fuel.
[0004]
However, when the fuel transported by the transport gas having a low oxygen concentration is ejected from the solid fuel burner, the combustion reaction does not proceed unless it is mixed with air. The combustion reaction is limited by the mixing speed of fuel and air, and the combustion speed is lower than that of bituminous coal that can be conveyed by air. Therefore, the burn-out time of the fuel becomes longer than the combustion of bituminous coal, and the unburned portion at the combustion device, that is, the outlet of the furnace increases.
[0005]
As a method for accelerating the ignition of the fuel conveyed by the carrier gas having a low oxygen concentration, there is a method for increasing the oxygen concentration of the fuel carrier gas by providing an additional air nozzle at the tip of the fuel nozzle. For example, Japanese Patent Laid-Open No. 10-73208 shows a solid fuel burner in which an additional air nozzle is provided outside the fuel nozzle.
[0006]
Further, as described in JP-A-11-148610, a solid fuel burner is also used in which an additional air nozzle is provided in the center of the fuel nozzle to promote mixing of fuel and air at the fuel nozzle outlet. .
[Problems to be solved by the invention]
[0007]
In the conventional solid fuel burner, an additional air nozzle is provided outside or inside the fuel nozzle to accelerate mixing of the solid fuel and air and promote a combustion reaction. When the additional air nozzle is provided in the fuel nozzle, it is desirable that the fuel jet composed of the mixed fluid of the solid fuel and the carrier gas and the air ejected from the additional air nozzle are sufficiently mixed at the fuel nozzle outlet.
[0008]
However, when the air ejected from the additional air nozzle is ejected in parallel with the fuel jet as in the above-described conventional example, the difference between the flow velocity of the fuel jet and the additional air is small, so the mixing of the fuel jet and the additional air is slow. Become.
[0009]
Usually, the distance from the additional air nozzle outlet to the fuel nozzle outlet is within 1 m. The flow velocity of the fuel jet is about 12 m / s or more. Therefore, the mixing time of the fuel particles and the additional air in the fuel nozzle is as short as about 0.1 second or less, and the fuel particles and the air cannot be sufficiently mixed.
[0010]
On the other hand, if the mixing time of the fuel particles and the additional air in the fuel nozzle is lengthened, there is a risk of a so-called flashback phenomenon that ignites in the fuel nozzle, so the distance from the additional air nozzle outlet to the fuel nozzle outlet is increased. Can't be long.
[0011]
Further, as described in Japanese Patent Application Laid-Open No. 11-148610, when a part of the additional air is ejected obliquely downstream from the tapered ejection portion, the additional air is unlikely to reach the outer peripheral portion of the fuel nozzle.
[0012]
Furthermore, in this conventional example, since the additional air injection port is provided in the rapid expansion portion of the flow path of the fuel nozzle, the flow of the mixed gas of the fuel and the carrier gas is disturbed, and a fuel concentration region is formed in the outer peripheral portion. Can not.
[0013]
An object of the present invention is to use a gas having a low oxygen concentration as a carrier gas for low-grade solid fuel such as lignite. solid In the fuel burner, the mixing of fuel particles and air in the fuel nozzle is promoted and stably burned over a wide range from high load conditions to low load conditions without changing the distance from the additional air nozzle outlet to the fuel nozzle outlet. A solid fuel burner with means is provided.
[0014]
Another object of the present invention is to provide a combustion method of a solid fuel burner provided with means for promoting stable mixing of the fuel particles and air, a combustion device including the solid fuel burner, and an operation method of the combustion device. Is to provide.
[Means for Solving the Problems]
[0015]
In order to achieve the above object, the present invention provides a fuel nozzle that ejects a mixed fluid of solid fuel and its carrier gas; A concentrator that is arranged on the center side of the fuel nozzle and comprises a portion for reducing the cross-sectional area of the flow passage in the fuel nozzle and a portion for increasing the size in order from the burner upstream side; An additional air nozzle that ejects air substantially perpendicular to the flow of the mixed fluid in the fuel nozzle, and at least one outer air nozzle that is disposed outside the fuel nozzle and ejects air, and an outlet of the additional air nozzle However, the burner upstream side of the fuel nozzle outlet And provided in the channel cross-sectional area enlarged portion by the concentrator A solid fuel burner is proposed.
[0016]
The additional air nozzle may be disposed in the center of the fuel nozzle, or may be disposed in a partition that separates the fuel nozzle and the outer air nozzle.
[0017]
You may provide the additional air nozzle which ejects air substantially perpendicular | vertical with respect to the flow of a mixed fluid in the flow-path cross-sectional area reduction part by a concentrator, or the flow-path expansion part downstream.
[0018]
It is also possible to provide the fuel nozzle partition wall with a flow path reducing member that once reduces the flow path cross-sectional area of the fuel nozzle in order from the burner upstream side and then expands to the original size.
[0019]
A swirler may be provided on the outer air nozzle.
[0020]
A guide for determining the jet direction of the outer air can be provided at the outer air nozzle outlet.
[0021]
A flame holder may be provided between the fuel nozzle and the outer air nozzle to block the flow of solid fuel ejected from the nozzle and its carrier gas and air, and a toothed flame holder is provided on the inner wall surface of the fuel nozzle outlet. It may be provided.
[0022]
When the combustion load is low, the amount of air supplied from the additional air nozzle is increased, and when the combustion load is high, a solid fuel burner combustion method is adopted in which the amount of air supplied from the additional air nozzle is reduced.
[0023]
If the combustion load is low, increase the amount of air supplied from the additional air nozzle, decrease the amount of air supplied from the outer air nozzle closest to the fuel nozzle among the outer air nozzles or increase the swirl flow rate, and if the combustion load is high Alternatively, a solid fuel burner combustion method may be employed in which the amount of air supplied from the additional air nozzle is reduced, the amount of air supplied from the air nozzle closest to the fuel nozzle among the outer air nozzles is increased, or the swirl strength is reduced.
[0024]
A combustion method of a solid fuel burner that increases the oxygen concentration in the outer peripheral portion relative to the central portion in the outlet cross section of the fuel nozzle can be adopted.
[0025]
You may employ | adopt the combustion method of the solid fuel burner which raises the oxygen concentration and fuel concentration of an outer peripheral part with respect to the center part in the exit cross section of a fuel nozzle.
[0026]
The present invention also includes any one of the above-described solid fuel burners, a fuel hopper, a coal feeder, and a downstream of the coal feeder that are installed so as to face at least two stages in the vertical direction and toward the center in the horizontal direction. A pulverizer that introduces fuel mixed with the flue gas extracted from the upper part of the combustion device in the flue gas piping on the side, and the fuel pulverized by the pulverizer solid Fuel piping for supplying to the fuel burner; solid A blower that supplies air to the fuel burner and low load conditions solid A low-load flame detector that monitors the flame formed for each fuel burner, and in high-load conditions solid A high-load flame detector that monitors the flame formed at a position away from the fuel burner, and a low-load flame detector or a high-load flame detector signal depending on the load and combustion method, and the supply amount of fuel and air A combustion apparatus comprising a control means for controlling the combustion is proposed.
[0027]
Combustion equipment is equipped with a thermometer or radiation intensity meter on the wall of the combustion equipment or solid The control means may be included in the fuel burner, and the control means may include means for adjusting the additional air flow rate based on the temperature signal.
[0028]
In any of the above combustion apparatus operating methods, when the combustion apparatus is operated at a high combustion load, a solid fuel flame is formed from a position away from the solid fuel burner, and the combustion apparatus is operated at a low combustion load. A solid fuel flame is formed immediately after the fuel nozzle exit of the solid fuel burner.
[0029]
The present invention provides a combustion apparatus provided with a plurality of the above-described solid fuel burners on a wall surface, and water is heated by combustion heat provided by combustion of solid fuel in the combustion apparatus, A coal-fired boiler equipped with a heat exchanger that generates heat is proposed.
[0030]
The solid fuel burner of the present invention is a solid fuel burner particularly suitable when a mixed fluid of a solid fuel having a low degree of coalification such as lignite and lignite and a carrier gas having an oxygen concentration lower than 21% is used.
[0031]
A solid fuel burner of the present invention includes a fuel nozzle that ejects a mixed fluid of a solid fuel and its carrier gas, an additional air nozzle that ejects air substantially perpendicular to the flow of the mixed fluid in the fuel nozzle, and a fuel nozzle A solid fuel burner having at least one outer air nozzle that ejects air disposed outside the fuel nozzle, the outlet of the additional air nozzle being located upstream of the outlet of the fuel nozzle.
[0032]
The additional air nozzle may be arranged in the center of the fuel nozzle or in the partition wall of the fuel nozzle.
[0033]
When the additional air jet ejected from the additional air nozzle is ejected substantially perpendicularly to the fuel jet, the speed difference between the fuel particles and the additional air jet becomes larger than that in the case of jetting in parallel, and mixing proceeds. In particular, since the fuel particles have a higher density than the gas, they are mixed in the additional air jet by inertia force.
[0034]
At this time, since the carrier gas having a low oxygen concentration around the fuel particles is separated from the fuel particles, the oxygen concentration around the fuel particles is higher than the oxygen concentration of the carrier gas. Therefore, after jetting from the fuel nozzle, the combustion reaction proceeds with a high oxygen concentration, and a flame is stably formed at the fuel nozzle outlet.
[0035]
At this time, in order to prevent backfire and burning due to the formation of flame in the fuel nozzle, it is desirable that the residence time of the fuel in the fuel nozzle is not longer than the ignition delay time (about 0.1 second) of the fuel. Usually, since the fuel carrier gas flows in the fuel nozzle at a flow rate of 12 to 20 m / s, the distance from the fuel nozzle outlet to the outlet of the additional air nozzle is 1 m or less.
[0036]
It is desirable to provide a flow path reducing member that once reduces the cross-sectional area of the nozzle in order from the burner upstream side and then expands to the original size on the inner wall of the fuel nozzle of the solid fuel burner of the present invention. When the flow path cross-sectional area is reduced, the flow velocity of the fuel carrier gas flowing in the fuel nozzle increases, so even if a flame is formed in the fuel nozzle due to a momentary drop in the flow velocity, Backfire can be prevented.
[0037]
Furthermore, if a concentrator comprising a portion for reducing the flow passage cross-sectional area of the fuel nozzle and a portion for enlarging the fuel nozzle in order from the upstream side of the burner is provided inside the fuel nozzle, the speed of the fuel particles toward the outer circumference along the concentrator Ingredients are induced. Since the fuel particles have an inertial force larger than that of the carrier gas, they flow toward the inner wall surface of the fuel nozzle and reach the nozzle outlet. As a result, a concentrated fuel jet is generated on the inner wall surface of the fuel nozzle.
[0038]
At this time, if air is ejected from the additional air nozzle in a direction substantially perpendicular to the fuel jet and the oxygen concentration is increased along the inner wall surface of the fuel nozzle, the fuel concentration is increased along the inner wall surface of the fuel nozzle and the oxygen concentration is increased. A region having a high concentration can be formed. As a result, after ejection from the fuel nozzle, the combustion reaction proceeds with a high oxygen concentration, and a flame can be stably formed at the fuel nozzle outlet.
[0039]
The pulverized coal flowing in the vicinity of the inner wall surface of the fuel nozzle is more likely to come into contact with the air ejected from the outer air nozzle in the vicinity of the fuel nozzle outlet. Moreover, it becomes easy to ignite in contact with a circulating high-temperature gas formed on the downstream side of the flame holder described later.
[0040]
The additional air nozzle may be ejected from the outer peripheral partition wall toward the center, or air may be ejected from the inside of the fuel nozzle toward the outside.
[0041]
The additional air nozzle is desirably provided in a portion where the flow path of the fuel nozzle is enlarged. Fuel particles have a higher inertial force than gas. Providing the additional air nozzle outlet at the flow channel expanding portion that hardly induces the velocity component from the flow channel toward the wall surface can suppress the fuel particles from entering or accumulating in the additional air nozzle.
[0042]
It is desirable to provide a flame holder for the flow of the solid fuel mixture and the air jetted from the fuel nozzle at the front ends of the partition walls of the fuel nozzle and the outer air nozzle. The pressure decreases on the downstream side of the flame holder, and a circulating flow is formed from the downstream to the upstream. In the circulation flow, air, fuel, fuel carrier gas ejected from the outer nozzle group, and hot gas from the downstream stay. As a result, the inside of the circulating flow becomes high temperature and acts as an ignition source for the fuel jet. Therefore, the flame is stably formed from the fuel nozzle outlet portion.
[0043]
Providing a toothed flame holder on the inner wall of the fuel nozzle outlet facilitates fuel ignition.
[0044]
The solid fuel burner of the present invention can change the amount of air ejected from the additional air nozzle according to the combustion load.
[0045]
When the combustion load is low, the amount of air ejected from the additional air nozzle is increased. At this time, since the oxygen concentration in the fuel nozzle is increased by the air ejected from the additional air nozzle, the combustion reaction of the fuel is accelerated as compared with the case where the oxygen concentration is low, and the ignition of the fuel is accelerated and the flame can be formed from the vicinity of the fuel nozzle. .
[0046]
When the combustion load is high, the amount of air ejected from the additional air nozzle is reduced. At this time, since the oxygen concentration in the fuel nozzle is low, the combustion reaction of the fuel does not proceed, the ignition of the fuel is delayed, and a flame can be formed at a position in the combustion apparatus away from the fuel nozzle.
[0047]
solid If the temperature of the fuel burner or the outer combustion unit wall is too high, solid A phenomenon called “slacking” occurs in which deposits grow on the fuel burner structure and the combustion apparatus wall.
[0048]
Flames according to the present invention solid When you leave the fuel burner, solid The temperature of the fuel burner and the combustion device wall outside the fuel burner is lowered, and slacking can be suppressed.
[0049]
In order to suppress the slacking, the amount of air ejected from the additional air nozzle is changed based on a signal from a thermometer or a radiation intensity meter provided on the solid fuel burner or the surrounding combustion apparatus wall.
[0050]
On the other hand, if the combustion load is low, solid The ratio of the total amount of air supplied from the fuel nozzle and the additional air nozzle of the fuel burner to the amount of air necessary for complete combustion of the volatile components in the fuel (the ratio of air to volatile components) is 0.85 to 0. It is desirable to adjust the amount of air so as to be .95.
[0051]
When the combustion load is low, stable combustion is difficult. Therefore, when the air ratio to the volatile component is set to 0.85 to 0.95, the flame temperature becomes high and stable combustion is easily maintained. By changing the amount of air, it is possible to adjust the amount of radiant heat to the solid fuel burner and the combustion device wall by changing the flame formation position in the combustion device.
[0052]
Under high load conditions, the heat load in the combustion device is high, solid It is desirable to form it at a position away from the fuel burner.
[0053]
According to the combustion method of the solid fuel burner of the present invention, in the high load condition of the combustion apparatus, solid Fuel is ignited at a position away from the fuel burner, and a flame is formed at the center of the combustion apparatus. solid To monitor the flame formed from the fuel burner, when operating under high load conditions, solid It is desirable to monitor the flame in the center of the combustion device where the fuel burner flame collects.
[0054]
Under low load conditions, the heat load in the combustor is low, so solid Even close to the fuel burner, solid The temperature of the fuel burner and the surrounding combustion apparatus wall is lower than in the case of high load conditions, and slacking hardly occurs.
[0055]
In the low load condition of the combustion device, solid The fuel ignites near the fuel burner to form a flame. At this time, individual solid A flame may be formed for each fuel burner, and the flame may be formed separately in the combustion apparatus. Therefore, it is desirable to monitor individual flames formed at individual solid fuel burner outlets at low load conditions.
[0056]
In the solid fuel burner of the present invention, a guide for determining the direction in which the outer air is ejected can be provided at the outlet of the outer air nozzle so that the outer air (secondary air, tertiary air) can be expanded and ejected from the burner central axis. At this time, the fuel spreads along the outside air, so the speed of the fuel near the burner decreases, solid Increased residence time near fuel burner. For this reason, the combustion efficiency in a combustion apparatus rises because the residence time of the fuel in a combustion apparatus increases.
[0057]
The outer air jet guides the guide from the outermost outermost air nozzle. solid If the angle is along the fuel burner or the outer combustion unit wall, the outside air will be solid The fuel burner and the combustion device wall outside the fuel burner can be cooled, and slacking can be suppressed.
[0058]
Examples of the combustion apparatus provided with a plurality of solid fuel burners of the present invention on the wall of the combustion apparatus include a coal fired boiler, a peat fired boiler, and a biomass (wood) fired boiler.
[0059]
The solid fuel burner of the present invention or solid Install a thermometer or radiation thermometer on the combustion device wall outside the fuel burner, and based on the signals from these measurement devices, solid When the combustion apparatus is operated so as to change the amount of air ejected from the additional air nozzle of the fuel burner, it is possible to control the flame to be formed at an appropriate combustion apparatus position in accordance with the change in the combustion load.
[0060]
For example, whether or not the flame is formed at an appropriate position is determined as follows. That is, when the combustion apparatus has a low load, the tip of the solid fuel flame in the combustion apparatus is formed near the combustion apparatus wall surface outside the fuel nozzle outlet. Operate the combustor so that a flame is formed at a position within the combustor at a distance of .5 m or more.
[0061]
When operating the combustion device at a high load, solid When the flame in the center of the combustion apparatus where the flame of the fuel burner gathers or in the vicinity thereof is monitored with a flame detector or visually, and the combustion apparatus is operated at a low load, solid The individual flames formed at the fuel burner outlet are monitored to ensure proper operation of the combustion system.
DETAILED DESCRIPTION OF THE INVENTION
[0062]
Next, an embodiment of a solid fuel burner, a combustion method of a solid fuel burner, a combustion apparatus equipped with a solid fuel burner, and an operation method of the combustion apparatus will be described with reference to FIGS.
Embodiment 1
[0063]
FIG. 1 is a cross-sectional view showing the structure of Embodiment 1 of the solid fuel burner according to the present invention. solid When using the fuel burner under low load conditions, solid It is a figure which shows the state which formed the flame of the fuel burner from the circulating flow vicinity of the downstream of a flame holder. FIG. 2 is a diagram illustrating a schematic structure of the solid fuel burner according to the first embodiment as viewed from the inside of the combustion device 41.
[0064]
The solid fuel burner of the first embodiment includes an auxiliary combustion oil gun 24 in the center, and a fuel nozzle 11 that ejects a mixed fluid of fuel and its carrier gas around the auxiliary combustion oil gun 24. Nozzle outlet from outer partition wall 22 of fuel nozzle 11 solid A plurality of additional air nozzles 12 are arranged in a direction toward the central axis of the fuel burner.
[0065]
An oil gun 24 for auxiliary combustion provided through the center of the fuel nozzle 11 is solid Used for fuel ignition when starting the fuel burner.
[0066]
Outside the fuel nozzle 11, there is an outer air nozzle (secondary air nozzle 13, tertiary air nozzle 14, etc.) for air ejection concentric with the fuel nozzle 11.
[0067]
An obstacle called a flame holder 23 is provided at the front end of the fuel nozzle 11, that is, at the combustion device outlet side. The flame holder 23 acts as an obstacle to the fuel jet 16 composed of the fuel ejected from the fuel nozzle 11 and the carrier gas and the secondary air flow 17 flowing through the secondary air nozzle 13. Therefore, the pressure on the downstream side of the flame holder 23, that is, the combustion device 41 side is lowered, and a flow in the opposite direction to the fuel jet 16 and the flow 17 of the secondary air is induced in this portion. This reverse flow is referred to as a circulating flow 19.
[0068]
In the circulating flow 19, hot gas generated by fuel combustion flows from the downstream and stays there. This hot gas and the fuel in the fuel jet 16 are solid When mixed in the combustion device 41 at the outlet of the fuel burner, the temperature of the fuel particles rises due to the radiant heat from the combustion device 41 and ignites.
[0069]
The secondary air nozzle 13 and the tertiary air nozzle 14 are separated by a partition wall 29, and a tip portion of the partition wall 29 forms a guide 25 that ejects the fuel air flow 16 so that the flow of the tertiary air 18 has an angle. It is. If a guide 25 that guides the direction in which the outer air is ejected away from the central axis of the burner is provided at the outlet of the flow path of the outer air nozzle (secondary air nozzle 13, tertiary air nozzle 14, etc.), the circulating flow is 19 to help form easily.
[0070]
In order to give a swirling force to the air ejected from the secondary air nozzle 13 and the tertiary air nozzle 14, swirlers 27 and 28 are provided in the nozzles 13 and 14.
[0071]
The burner throat 30 constituting the combustion device wall also serves as the outer peripheral wall of the tertiary air nozzle. A water pipe 31 is provided on the combustion apparatus wall.
[0072]
In the first embodiment, combustion exhaust gas is used as the fuel carrier gas, and the oxygen concentration in the fuel jet 16 flowing through the fuel nozzle 11 is lowered. As an example of applying such a combustion method, there is combustion of lignite or lignite.
[0073]
Compared with coal with high degree of coalification such as bituminous coal and anthracite, calorific value is low, and generally pulverization is poor. Furthermore, the melting temperature of combustion ash is low. Since these fuels have a large amount of volatile components, they tend to spontaneously ignite in the air atmosphere during storage and pulverization, and are difficult to handle compared to bituminous coal. In order to prevent spontaneous ignition, when lignite or lignite is pulverized and burned, a mixed gas of combustion exhaust gas and air is used as a fuel carrier gas. Combustion exhaust gas reduces oxygen concentration and prevents spontaneous ignition of fuel. Further, moisture in the fuel can be evaporated by the retained heat of the combustion exhaust gas.
[0074]
Under a low oxygen concentration atmosphere, the burning rate is slower than the burning rate in air. When pulverized coal such as lignite and lignite is transported with a carrier gas having a low oxygen concentration, the combustion speed is limited by the mixing speed of fuel and air, and the combustion speed is lower than that of bituminous coal that can be transported by air. For this reason, the amount of fuel combustion is small solid When lignite, lignite, or the like is burned under a low load condition of the fuel burner, the flame 20 is likely to blow off or misfire more than in the case of burning bituminous coal.
[0075]
In the first embodiment, the fuel nozzle 11 has an additional air nozzle 12 that ejects air substantially perpendicular to the fuel jet. When the air jet (additional air jet) 21 ejected from the additional air nozzle 12 is ejected at a substantially right angle to the fuel jet, the speed difference between the fuel particles and the air becomes larger than when jetted in parallel, and the mixing proceeds. In particular, since the fuel particles have a higher density than the gas, they are mixed in the additional air jet by inertia.
[0076]
At this time, since the carrier gas (low oxygen concentration) around the fuel particles is separated from the fuel particles, the oxygen concentration around the fuel particles is higher than that of the carrier gas. For this reason, after ejection from the fuel nozzle, the combustion reaction easily proceeds due to the high oxygen concentration, and the flame 20 is stably formed at the fuel nozzle outlet.
[0077]
The distance from the outlet of the fuel nozzle to the outlet of the additional air nozzle 12 is determined so that the residence time of the fuel in the fuel nozzle 11 is approximately the ignition delay time of the fuel in order to prevent backfire and burning due to the formation of the flame 20 in the fuel nozzle 11. It is desirable that the length be 0.1 second or less. Usually, since the fuel carrier gas flows through the fuel nozzle at a flow rate of 12 to 20 m / s, the distance is 1 m or less.
[0078]
Furthermore, in the first embodiment, the flow path reducing member 32 that reduces the flow path provided in the fuel nozzle 11 is provided in the outer partition wall 22 on the upstream side of the fuel nozzle 11. An obstacle (concentrator) 33 is provided outside the oil gun 24 at the center of the fuel nozzle for temporarily reducing the flow path in the fuel nozzle 11 and then expanding it. The obstacle 33 is more than the flow path reducing member 32. solid It is provided on the downstream side (combustion device 41 side) of the fuel burner.
[0079]
The flow path reducing member 32 induces a velocity component in the direction of the central axis of the fuel nozzle in fuel particles (pulverized coal) having an inertial force larger than that of the fuel carrier gas. When the concentrator 33 is provided on the downstream side of the flow path reducing member 32, the flow of fuel particles (pulverized coal) squeezed by the flow path reducing member 32 in the burner central axis direction passes through the concentrator 33 and then the fuel nozzle 11. It flows toward the partition wall 22 along the flow path. Since the fuel particles (pulverized coal) flowing along the flow path in the fuel nozzle have an inertial force larger than that of the fuel carrier gas, the fuel particles flow toward the inner wall surface (partition wall 22) of the fuel nozzle 11 and go to the outlet. Therefore, the fuel is concentrated on the inner wall surface (partition wall 22) side of the fuel nozzle 11.
[0080]
Since the air ejected from the additional air nozzle is also ejected toward the inner wall surface (partition wall 22) of the fuel nozzle 11, a region having a high fuel concentration and a high oxygen concentration is formed. As a result, after the fuel is ejected from the fuel nozzle 11, the combustion reaction easily proceeds due to the high oxygen concentration, and the flame 20 is stably formed at the fuel nozzle outlet. The fuel jet flowing on the inner wall surface (partition wall 22) side of the fuel nozzle 11 is easily mixed with the air jetted from the outer air nozzle in the vicinity of the fuel nozzle 11 outlet.
[0081]
Further, when mixed with a circulating high-temperature gas formed on the downstream side of the flame holder 23, the temperature of the fuel particles rises and ignition is easy. As a result, the flame 20 is stably formed at the fuel nozzle outlet.
[0082]
When the air is ejected from the additional air nozzle 12 substantially perpendicularly to the fuel jet flowing in the fuel nozzle 11, the mixing of the fuel particles and the air proceeds and the flame 20 is stably formed at the fuel nozzle outlet. Therefore, combustion can be continued stably at a lower load than in the past.
[0083]
When burning lignite and lignite with high heat load, there are many volatile components under conditions where air and fuel are well mixed. solid The amount of fuel burned near the fuel burner increases. in this way, solid The heat load near the fuel burner increases locally, and radiant heat from the flame 20 solid When the fuel burner structure and the combustion apparatus wall become high temperature, the combustion ash adheres and melts, and there is a risk of causing slacking. In particular, lignite and lignite have a low melting temperature of combustion ash, and thus are prone to slacking.
[0084]
In the first embodiment, solid Change the formation position of the flame 20 according to the load of the fuel burner, when using fuel with a low degree of coalification solid To solve the problem caused by the combustion state being different between the high and low load conditions of the fuel burner. That is, under high load conditions solid The flame 20 is formed at a position away from the fuel burner, and the flame 20 is formed near the outlet of the fuel nozzle 11 under a low load condition. Under low load conditions, the flame 20 may be solid Even if it is close to the fuel burner, the heat load in the combustion device 41 is low. solid The temperature of the fuel burner and the surrounding combustion device wall is lower than in the case of high load conditions. Therefore, no slacking occurs.
[0085]
In the first embodiment, under the low load condition, the flame 20 is formed near the outlet of the fuel nozzle 11, and the high temperature gas is retained in the circulating flow 19 formed on the downstream side of the flame holder 23 and the guide 25. Further, the flow control valve 34 of the additional air nozzle 12 is opened to supply air, and the oxygen concentration in the fuel jet 16 near the flame holder 23 is increased. As a result, since the combustion speed is higher than when the oxygen concentration is low, the ignition of the fuel particles is accelerated, and the flame 20 can be formed from the vicinity of the fuel nozzle 11.
[0086]
Under high load conditions solid The flame 20 is formed at a position away from the fuel burner, solid Reduce the heat load near the fuel burner. For this reason, in this Embodiment 1, the flow rate adjustment valve 34 of the additional air nozzle 12 is closed, and an air supply amount is reduced compared with the case of a low load condition. At this time, the oxygen concentration in the fuel jet 16 near the flame holder 23 becomes lower than that in the low load condition, and the combustion speed also becomes slower. For this reason, the temperature of the circulating flow 19 that is made downstream of the flame holder 23 is lowered, solid The radiant heat received by the fuel burner structure can be reduced, and slacking can be suppressed.
[0087]
FIG. 3 shows the first embodiment. solid When using the fuel burner under high load conditions, solid It is a figure which shows the state which formed the flame 20 of the fuel burner away from the circulation flow 19 of the downstream of the flame holder 23.
[0088]
FIG. 4 is a horizontal sectional view showing the structure of a combustion apparatus using the solid fuel burner 42 of the first embodiment. When the solid fuel burner 42 is used under a high load condition as shown in FIG. 3, it is desirable that the flame 20 is stably burned by mixing the flames 20 in the combustion device 41 in order to reduce the risk of misfire.
[0089]
In FIG. solid Although the fuel burner 42 is shown at the four corners of the combustion device wall, solid The same applies to the case of the opposed combustion system in which the fuel burner 42 is disposed on the opposed combustion device wall.
[0090]
In order to reduce nitrogen oxides NOx generated by combustion, the ratio between the total amount of air supplied from the fuel nozzle 11 and the additional air nozzle 12 and the amount of air required to completely burn volatiles in the fuel ( It is desirable to adjust the amount of air so that the ratio of air to volatile components is from 0.85 to 0.95.
[0091]
Most of the fuel is mixed with the air supplied from the nozzles contained in the fuel nozzle 11 and burned (first stage), and then the secondary air 17 and the tertiary air flow 18 are mixed and burned. (Second stage). further, solid When an after-air port 49 (see FIG. 11) for supplying air is installed in the combustion device 41 on the downstream side of the fuel burner, the fuel is mixed with the air supplied from the after-air port 49 and completely burned ( Third stage). The volatile matter in the fuel burns in the first stage because it has a higher combustion speed than fixed carbon.
[0092]
At this time, if the air ratio to the volatile component is 0.85 to 0.95, the combustion of the fuel is promoted and combustion can be performed at a high flame temperature although oxygen is insufficient. In the combustion in the first stage, the fuel is reduced and burned with oxygen shortage, so nitrogen oxide (NOx) generated from nitrogen in the fuel and nitrogen in the air is converted into harmless nitrogen and discharged from the combustion device 41 The amount of NOx produced can be reduced. Since the fuel reacts at a high temperature, the second stage reaction is promoted and the unburned portion can be reduced.
[0093]
In the first embodiment solid The fuel burner has a circular shape in which cylindrical fuel nozzles 11, secondary air nozzles 13, and tertiary air nozzles 14 are arranged concentrically as shown in FIG.
[0094]
FIG. solid It is a figure which shows another example of the nozzle part of a fuel burner. When the fuel nozzle 11 is square, the concentrator 33 is square, or at least some of the outer air nozzles such as the secondary air nozzle 13 and the tertiary air nozzle 14 are installed so as to sandwich the fuel nozzle 11. An air nozzle structure may be used. A case where the outside air is supplied from one nozzle or a nozzle structure divided into three or more may be used.
Embodiment 2
[0095]
FIG. 6 is a cross-sectional view showing the structure of Embodiment 2 of the solid fuel burner according to the present invention in which the installation position of the additional air nozzle is changed. As shown in FIG. 1, the additional air nozzle 12 may eject air from the outer peripheral partition wall toward the center, as shown in FIG. 6, instead of ejecting air from the inside of the fuel nozzle toward the outside.
[0096]
The additional air nozzle 12 is desirably provided in a portion where the flow path of the fuel nozzle 11 expands. Providing the outlet of the additional air nozzle 12 at the channel expansion portion where it is difficult to induce a velocity component from the channel toward the wall surface can prevent fuel particles from entering or depositing in the additional air nozzle.
[0097]
In order to prevent the fuel nozzle 11 from being burned out and back-fired due to the ignition of fuel in the fuel nozzle 11, the additional air nozzle is set so that the residence time of the fuel in the fuel nozzle 11 is shorter than the fuel ignition delay time. It is desirable to determine 12 arrangements. Usually, the ignition delay time of the gas fuel having an ignition delay time shorter than that of pulverized coal or the like is about 0.1 second, and the flow velocity in the fuel nozzle 11 is 10 to 20 m / s. For example, the distance between the outlet of the fuel nozzle 11 and the outlet of the additional air nozzle 12 is set within about 1 m.
Embodiment 3
[0098]
FIG. 7 does not have the concentrator 33 solid It is sectional drawing which shows the structure of Embodiment 3 of a fuel burner. In the first embodiment, the concentrator 33 is provided in the fuel nozzle 11. However, as shown in FIG. When the air to be ejected is ejected, the fuel jet and air in the fuel nozzle 11 are mixed in the same manner as in the first embodiment.
Embodiment 4
[0099]
8 and 9 are according to the invention. solid It is sectional drawing which shows the structure of Embodiment 4 of a fuel burner. FIG. 8 is in a low load condition solid FIG. 9 shows a state in which the fuel ejected from the fuel burner is combusted in the combustion device 41, and FIG. 9 is under a high load condition. solid The state in which the fuel ejected from the fuel burner is combusting in the combustion device 41 is shown.
[0100]
The main difference between the fourth embodiment and the first embodiment is that the flame holder 23 and the guide 25 are not provided at the tip of the outer partition wall 22 of the fuel nozzle 11. In the fourth embodiment, the swirler 27 provided in the secondary air flow path is used to change the shape of the flame 20 without providing the flame holder 23 and the guide 25.
[0101]
Under low load conditions, air is supplied from the additional air nozzle 12 to increase the oxygen concentration in the fuel jet 16 near the outer partition wall 22 of the fuel nozzle 11. Since the combustion speed is higher than when the oxygen concentration is low, the ignition of the fuel particles is accelerated, and the flame 20 can be formed from the vicinity of the fuel nozzle 11.
[0102]
In the fourth embodiment, the swirler 27 provided in the secondary air flow path gives a strong swirl flow velocity (usually 1 or more in swirl number) to the secondary air. The secondary air flow 17 spreads in a direction away from the fuel jet 16 after being ejected from the secondary air nozzle 13 by the centrifugal force generated by the swirling flow velocity. At this time, the pressure is reduced in the region between the fuel jet 16 and the secondary air flow 17, and a circulation flow 19 is induced that is a flow in the opposite direction to the fuel jet 16 and the secondary air flow 17. When a damper for reducing the flow rate is attached to the secondary air flow path and the flow rate of the secondary air is reduced to near zero, a circulation flow can be induced between the tertiary air flow 18 and the fuel jet 16.
[0103]
Under high load conditions, flame 20 solid It is formed at a position away from the fuel burner, solid Reduce the heat load near the fuel burner. For this reason, compared with the case of a low load condition, the air supply amount from the additional air nozzle 12 is reduced. When the supply amount of the additional air decreases, the oxygen concentration in the fuel jet 16 becomes lower near the outer partition wall 22 of the fuel nozzle 11 than in the low load condition, and the combustion speed also becomes slower.
[0104]
Furthermore, in this Embodiment 4, the swirl | vortex flow velocity given to secondary air is weakened with the swirler 27 provided in the secondary air flow path. Since the secondary air flow 17 flows in parallel with the fuel jet 16 after being ejected from the secondary air nozzle 13, the flow is in the opposite direction in the region between the fuel jet 16 and the secondary air flow 17. Circulation flow 19 does not occur. When the damper attached to the secondary air flow path is opened and the flow rate of the secondary air is increased, the circulating flow 19 that is the reverse flow is not generated in the region between the fuel jet 16 and the secondary air flow 17. Can be.
[0105]
FIG. 10 is a diagram showing an example of another structure of the flame holder. In the fourth embodiment, as shown in FIG. 10, a toothed flame holder 54 may be provided. The fuel goes around the toothed flame holder 54 to facilitate ignition. That is, it ignites behind the toothed flame holder 54.
Embodiment 5
[0106]
FIG. 11 is a diagram showing a schematic structure of a combustion apparatus using a solid fuel burner according to the present invention, and FIG. 12 is a horizontal sectional view of the combustion apparatus of FIG.
[0107]
In the fifth embodiment, the combustion device (furnace) 41 has two stages in the vertical direction and in the horizontal direction from the four corners of the combustion device 41 toward the center. solid A fuel burner 42 is installed. The fuel is supplied from the fuel hopper 43 to the pulverizer 45 through the coal feeder 44. At this time, the fuel is mixed with the combustion exhaust gas extracted from the upper part of the combustion device 41 in the combustion exhaust gas pipe 55 on the downstream side of the coal feeder 44 and introduced into the pulverizer 45. The fuel pulverized by the pulverizer 45 passes through the fuel pipe 56. solid It is supplied to the fuel burner 42.
[0108]
When the fuel is mixed with high-temperature combustion exhaust gas, moisture contained in the fuel evaporates. Further, when the combustion exhaust gas is mixed with fuel, the oxygen concentration decreases, so that spontaneous ignition and explosion can be suppressed even when the temperature is high when pulverizing with the pulverizer 45. In the case of lignite, the oxygen concentration is often about 8 to 15%. solid Air is supplied from the blower 46 to the fuel burner 42 and an after air port 49 provided downstream thereof.
[0109]
In the fifth embodiment, solid A two-stage combustion method is used in which less air than the amount necessary for complete combustion of fuel is supplied from the fuel burner 42 and the remaining air is supplied from the after air port 49.
[0110]
The present invention does not provide the after-air port 49, solid The present invention can also be applied to a single-stage combustion method in which all necessary air is supplied from the fuel burner 42.
[0111]
solid In the fuel burner 42, the combustion method is changed according to the load of the combustion device 41. That is, under high load conditions, the flame 20 is solid Formed at a position away from the fuel burner 42; solid The heat load near the fuel burner 42 is reduced. Under the low load condition, the flame 20 is formed near the outlet of the fuel nozzle 11. At this time, it is necessary to monitor the flame 20 in order to safely operate the combustion apparatus.
[0112]
In the present invention, since the combustion method changes with the load, it is desirable to change the monitoring method. In other words, under low load conditions solid In order to monitor the flame 20 formed for each fuel burner 42, the low-load flame detector 47 is individually connected. solid Installed in the fuel burner 42. Under high load conditions solid In order to form the flame 20 at a position away from the fuel burner 42, it is necessary to install a high-load flame detector 48 for monitoring the center of the combustion apparatus. Control means for selecting the signal of the low load flame detector 47 or the high load flame detector 8 in accordance with the load and the combustion method and controlling the supply amount of fuel and air is provided.
[0113]
Furthermore, under high load conditions solid In order to reduce the slack to the fuel burner structure and the combustor wall, a thermometer or a radiation intensity meter (not shown) solid It is also possible to install the fuel burner 42 and adjust the additional air flow rate based on the signal.
【The invention's effect】
[0114]
According to the present invention, even in the case of a solid fuel with relatively low combustibility such as coal with a low degree of coalification such as lignite and lignite, high load conditions without changing the distance from the outlet of the additional air nozzle to the outlet of the fuel nozzle Thus, a solid fuel burner having means for promoting the mixing of fuel particles and air in the fuel nozzle in a wide range from a low load condition to a stable combustion and preventing the slack caused by the combustion ash can be obtained.
[0115]
Also, a combustion method of a solid fuel burner having means for promoting the mixing of fuel particles and air to achieve stable combustion and preventing slacking caused by combustion ash, a combustion device having a solid fuel burner, and operation of the combustion device Method, coal fired boiler is obtained.
[Brief description of the drawings]
[0116]
FIG. 1 is a sectional view showing the structure of a first embodiment of a solid fuel burner according to the present invention. solid When using the fuel burner under low load conditions, solid It is a figure which shows the state which formed the flame of the fuel burner from the circulating flow vicinity of the downstream of a flame holder.
FIG. 2 is a view showing a schematic structure of the solid fuel burner according to the first embodiment as viewed from the inside of the combustion apparatus.
FIG. 3 shows the first embodiment. solid When using the fuel burner under high load conditions, solid It is a figure which shows the state which formed the flame of the fuel burner away from the circulation flow of the downstream of a flame holder.
FIG. 4 is a horizontal sectional view showing a structure of a combustion apparatus using the solid fuel burner of Embodiment 1.
[Figure 5] solid It is a figure which shows another example of the nozzle part of a fuel burner.
FIG. 6 is a cross-sectional view showing the structure of Embodiment 2 of the solid fuel burner according to the present invention in which the installation position of the additional air nozzle is changed.
[Fig. 7] Without a concentrator solid It is sectional drawing which shows the structure of Embodiment 3 of a fuel burner.
FIG. 8 is according to the present invention. solid It is sectional drawing which shows the structure of Embodiment 4 of a fuel burner, and is in a low load condition solid It is a figure which shows the state which the fuel injected from a fuel burner is combusting with a combustion apparatus.
FIG. 9 is according to the present invention. solid It is sectional drawing which shows the structure of Embodiment 4 of a fuel burner, and exists in a high load condition solid It is a figure which shows the state which the fuel injected from a fuel burner is combusting with a combustion apparatus.
FIG. 10 is a diagram showing another example of the structure of the flame holder.
FIG. 11 is a view showing a schematic structure of a combustion apparatus using a solid fuel burner according to the present invention.
12 is a horizontal sectional view of the combustion apparatus of FIG. 11. FIG.
[Explanation of symbols]
[0117]
11 Fuel nozzle
12 Additional air nozzle
13 Secondary air nozzle (outside air nozzle)
14 Tertiary air nozzle (outside air nozzle)
16 Flow of fuel and its carrier gas (fuel jet)
17 Flow of secondary air
18 Flow of tertiary air
19 Circulating flow
20 flame
21 Additional air flow
22 Outer bulkhead of fuel nozzle
23 Obstacle (flame holder)
24 oil gun
25 Guide
26 Windbox
27 Swivel
28 Swivel
29 Bulkhead,
30 Burner Throat
31 water pipe
32 Channel reduction member (Venturi)
33 Obstacle (concentrator)
34 Flow control valve
41 Combustion device (furnace)
42 solid Fuel burner
43 Fuel hopper
44 coal feeder
45 Crusher
46 Blower
47 Low load flame detector
48 High load flame detector
49 After Airport
54 Toothed flame holder
55 Combustion exhaust gas piping
56 Fuel piping

Claims (19)

A fuel nozzle that ejects a mixed fluid of solid fuel and its carrier gas;
A concentrator which is arranged on the center side of the fuel nozzle and comprises a portion for reducing the cross-sectional area of the flow passage in the fuel nozzle and a portion for increasing the size in order from the burner upstream side;
An additional air nozzle for injecting air into the fuel nozzle substantially perpendicular to the flow of the mixed fluid;
At least one outer air nozzle that is disposed outside the fuel nozzle and ejects air;
The solid fuel burner characterized in that the outlet of the additional air nozzle is provided on the upstream side of the burner with respect to the outlet of the fuel nozzle, and is provided in the channel cross-sectional area enlarged portion by the concentrator . The solid fuel burner according to claim 1,
A solid fuel burner using a gas having an oxygen concentration lower than that of air as the carrier gas. The solid fuel burner according to claim 1,
  A solid fuel burner using a mixed gas of combustion exhaust gas and air as the carrier gas. The solid fuel burner according to claim 1,
A solid fuel burner, wherein the additional air nozzle is disposed at a central portion of the fuel nozzle. The solid fuel burner according to claim 1,
The solid fuel burner, wherein the additional air nozzle is disposed in a partition wall that separates the fuel nozzle and the outer air nozzle. In the solid fuel burner according to any one of claims 1 to 5,
A solid fuel burner, characterized in that a flow path reduction member is provided in a partition wall of the fuel nozzle in order from the upstream side of the burner, once the flow path cross-sectional area of the fuel nozzle is reduced and then expanded to the original size. The solid fuel burner according to any one of claims 1 to 6,
A solid fuel burner characterized in that a swirler is provided in the outer air nozzle. The solid fuel burner according to any one of claims 1 to 7,
A solid fuel burner characterized in that a guide for determining the direction of ejection of outside air is provided at the outlet of the outside air nozzle. The solid fuel burner according to any one of claims 1 to 8,
Solid fuel burner, characterized in that a flame holder to prevent the solid material fuel and the flow of the carrier gas or air between the outer air nozzle and the fuel nozzle. The solid fuel burner according to claim 9,
A solid fuel burner, wherein a toothed flame holder is provided on an inner wall surface of the fuel nozzle outlet. In the combustion method of the solid fuel burner according to any one of claims 1 to 10,
If the combustion load is low, increase the amount of air supplied from the additional air nozzle,
A combustion method for a solid fuel burner, characterized in that when the combustion load is high, the amount of air supplied from the additional air nozzle is reduced. In the combustion method of the solid fuel burner according to any one of claims 1 to 10,
If the combustion load is low, increase the amount of air supplied from the additional air nozzle,
To reduce the amount of air supplied from the nearest outer air nozzle to the fuel nozzle among said outer air nozzles,
If the combustion load is high, the additional air reduces the amount of air supplied from the nozzle, the solid fuel burners, characterized in increasing and to be an amount of air supplied from the nearest air nozzle to the fuel nozzle among said outer air nozzles Combustion method. In the combustion method of the solid fuel burner according to any one of claims 1 to 10,
If the combustion load is low, increase the amount of air supplied from the additional air nozzle,
Reducing the amount of air supplied from the outer air nozzle closest to the fuel nozzle among the outer air nozzles and increasing the swirl flow velocity;
If the combustion load is high, characterized in that reducing the additional air reduces the amount of air supplied from the nozzle, the turning velocity with increasing and to the amount of air supplied from the nearest air nozzle to the fuel nozzle among said outer air nozzles A method for burning a solid fuel burner. The method for burning a solid fuel burner according to any one of claims 11 to 13 ,
A method for burning a solid fuel burner, wherein an oxygen concentration in an outer peripheral portion is increased with respect to a central portion in an outlet cross section of the fuel nozzle. The method for burning a solid fuel burner according to any one of claims 11 to 13 ,
A combustion method of a solid fuel burner, wherein an oxygen concentration and a fuel concentration in an outer peripheral portion are increased with respect to a central portion in an outlet cross section of the fuel nozzle. The solid fuel burner according to any one of claims 1 to 10, which is installed so as to face at least two stages in the vertical direction and toward the center in the horizontal direction.
A fuel hopper,
A coal feeder,
A pulverizer for introducing fuel mixed with the combustion exhaust gas extracted from the upper part of the combustion apparatus in the combustion exhaust gas pipe on the downstream side of the coal feeder;
A fuel pipe for supplying fuel crushed by the pulverizer to the solid fuel burner;
A blower for supplying air to the solid fuel burner;
A low load flame detector for monitoring the flame formed for each solid fuel burner under low load conditions;
A high-load flame detector for monitoring a flame formed at a position away from the solid fuel burner in a high-load condition;
A combustion apparatus comprising control means for controlling a supply amount of fuel and air by selecting a signal of a low load flame detector or a high load flame detector according to a load and a combustion method. The combustion device according to claim 16 , wherein
A thermometer or radiation intensity meter is installed on the wall of the combustion device or the solid fuel burner;
The combustion apparatus characterized in that the control means includes means for adjusting an additional air flow rate based on a temperature signal. The operation method of the combustion apparatus according to claim 16 or 17 ,
When operating the combustion device at a high combustion load, form a solid fuel flame from a position away from the solid fuel burner,
When operating the said combustion apparatus with a low combustion load, the flame of a solid fuel is formed immediately after the fuel nozzle exit of a solid fuel burner, The operating method of the combustion apparatus characterized by the above-mentioned. A combustion apparatus comprising a plurality of wall surfaces of the solid fuel burner according to any one of claims 1 to 10,
A coal-fired boiler provided with a heat exchanger that is provided in the combustion device and heats water with combustion heat generated by combustion of solid fuel in the combustion device to generate steam.

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