JP4341131B2 - Pulverized coal blowing burner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a burner that burns pulverized coal with oxygen gas. The pulverized coal is used as an inexpensive fuel or reducing agent in a blast furnace and other wide-ranging industrial reaction furnaces or industrial reaction vessels, or industrial heating furnaces. The present invention relates to a pulverized coal burner for efficient combustion.
[0002]
[Prior art]
Coke used in blast furnace smelting acts as a fuel and iron ore reducing agent in the blast furnace, and the raw material for this coke is high-quality caking coal. However, this caking coal is expensive and does not have much reserves. Therefore, in order to reduce the amount of coking coal used for blast furnace coke, a so-called pulverized coal injection operation in which non-caking coal with a low price and abundant reserves is directly injected into the blast furnace in the form of pulverized coal as an alternative. Technical development is being carried out to inject as much pulverized coal as possible.
[0003]
Conventionally, as a method of blowing pulverized coal into the blast furnace, a so-called pulverized coal burner is inserted obliquely from the outside into the straight pipe portion of the blast branch pipe in front of the tuyere at the bottom of the blast furnace, and pulverized coal is blown into hot air, which is oxygen gas A method of blowing into the furnace while burning is known.
[0004]
However, since pulverized coal is a pulverized solid fuel, it is inferior in combustibility compared with, for example, liquid fuel such as heavy oil. Therefore, in order to improve the combustibility, the oxygen concentration in the blower is increased, the blower temperature is raised, and the burner is installed as far as possible from the tuyere to flow into the furnace from the tuyere. In the meantime, measures such as promoting the combustion of pulverized coal have been taken.
[0005]
However, the ash contained in the pulverized coal becomes a molten state at a high temperature associated with the combustion of the pulverized coal, adheres to the inner surface of the tuyere, narrows or deforms the tuyere diameter, and blows air from the tuyere. This impairs controllability, which makes it difficult to control the reaction in the furnace and impairs the stability of blast furnace operation. In addition, accumulation of unburned pulverized coal in the furnace lowers the ventilation of the furnace, leading to deterioration of the furnace condition.
[0006]
Therefore, the design of pulverized coal burner and its proper use is to improve the flammability of pulverized coal, prevent the generation of unburned pulverized coal, increase the amount of pulverized coal injection while ensuring the stability of blast furnace operation This is an extremely important issue.
[0007]
For example, Japanese Patent Application Laid-Open No. 7-23489 discloses a pulverized coal burner that can blow a large amount of pulverized coal while improving flammability of pulverized coal and preventing ash from adhering to the inner surface of the tuyere. For the purpose of development, pulverized coal is ejected from the central part including the axis line of the burner, oxygen gas is ejected from a plurality of holes surrounding the periphery, and the axis line of the pulverized coal and oxygen gas is connected to the nozzle of the burner. Propose a pulverized coal burner to mix and burn both in front of the tip, and insert this pulverized coal burner diagonally from the outside into the straight pipe part of the blast branch pipe connected to the blast furnace lower tuyere, A technique for injecting and burning the mixed fluid into hot air (hereinafter referred to as “prior art 1”) is disclosed.
[0008]
Further, in JP-A-1-268890, in blast furnace operation with high oxygen concentration blast gas, a window for observation inside the furnace is provided in the shaft core portion of the pulverized coal burner, and information obtained from this is controlled in the furnace heat or Input for blast furnace calculation control to ensure stable operation of the blast furnace, and to inject a large amount of pulverized coal without deteriorating the furnace condition and shortening the tuyere life, The furnace observation tube is provided, and on the outside, a pulverized coal injection tube, a tuyere tip temperature adjustment gas tube for injecting gas for adjusting the temperature of the tuyere tip, and an oxygen gas tube are slit concentrically. A pulverized coal burner having a nozzle tube in the form is disclosed. And the traveling direction of the mixed fluid of pulverized coal and various gases is designed in a structure directed to the inside of the furnace from the position of a predetermined distance before the tuyere outlet to improve combustibility (hereinafter, "Prior art 2").
[0009]
[Problems to be solved by the invention]
When pulverized coal is blown into a blast furnace as an alternative to coke, it is important to develop a burner for pulverized coal injection that can increase the amount of pulverized coal injected at low cost while ensuring stable operation of the blast furnace. Therefore, the performance that the pulverized coal burner should have is to improve the combustion characteristics of the pulverized coal described above, thereby preventing the generation of unburned pulverized coal and preventing the deterioration of air permeability in the furnace, and a certain amount of oxygen It is important that a large amount of pulverized coal can be blown in while reducing the amount of oxygen used by increasing the amount of pulverized coal combusted by gas (hereinafter referred to as “pulverized carbon dioxide ratio”). Furthermore, it is necessary to design to prevent the deformation and reduction of the tuyere cross-sectional shape and dimensions due to fusion / deposition of ash in pulverized coal on the inner surface of the tuyere.
[0010]
Neither the prior art 1 nor the prior art 2 can sufficiently solve the above problem. That is, in the prior art 1, the pulverized carbon dioxide ratio that enables pulverized coal injection without fusion / deposition of ash to the tuyere does not reach a sufficiently satisfactory level. For example, when calculating the pulverized carbon dioxide ratio when the amount of pulverized coal injection is maximized under the condition that no ash fusion / deposition occurs at the tuyere, using the numerical values in the examples described in the publication 0.70 kg-pulverized coal / Nm ³ —O ₂ gas. In Prior Art 2, uniform processing of concentric slit nozzles is difficult, and in particular, the oxygen gas flow ejected at a high speed of about 300 to 350 m / s tends to be uneven in the circumferential direction. In this way, when the gas flow rate is increased, a drift occurs in the ejected gas, the miscibility of pulverized coal and each gas is reduced, and the combustion characteristics are deteriorated. Therefore, since the flow rate of oxygen gas cannot be increased sufficiently, there is a limit in increasing the amount of pulverized coal injection.
[0011]
The object of the present invention is to solve the above-mentioned problems, to achieve good flammability, to enable a large amount of pulverized coal injection, to increase the pulverized carbon dioxide ratio, and to reduce the amount of oxygen gas used. The aim is to develop burners for burn-in combustion.
[0012]
[Means for Solving the Problems]
As a result of intensive research from the viewpoints described above, the inventors of the present application have pulverized coal by blowing a pulverized coal with a cylindrical fluid from an annular slit nozzle and blowing a high-speed oxygen gas from a nozzle hole to form a mixed fluid. In addition, the tuyere tip temperature adjusting gas is injected without disturbing the formation of the mixed fluid, and the combustion state is observed through an appropriately provided observation tube in the furnace. It has been found that if the state is controlled, high-efficiency combustion is performed by mixed combustion of pulverized coal and pure oxygen gas. Furthermore, it was found that if the formation region of the mixed fluid is set in the inner side of the furnace than the tuyere attached to the tip of the burner, the fused ash is accumulated in the tuyere and does not cause an operation trouble.
[0013]
The present invention has been made based on the above findings, and the gist thereof is as follows.
[0014]
The pulverized coal blowing burner according to claim 1 is provided with an in-furnace observation hole in a central portion including an axial core line of the burner, and in a slit form for blowing pulverized coal concentrically outside the in-furnace observation hole. A pulverized coal injection nozzle is provided, and a plurality of tuyere tip temperature adjustment gas nozzles are provided on a concentric circle outside the pulverized coal injection nozzle to jet gas for adjusting the temperature of the tuyere tip of the furnace. A plurality of oxygen gas nozzles for injecting oxygen gas are arranged side by side on a concentric circle outside the tuyere tip temperature control gas nozzle, and at least one of the tuyere tip temperature control gas nozzle and the oxygen gas nozzle is configured by a circular pipe And the pulverized coal injection nozzle and the oxygen gas nozzle are provided with an injection direction of a cylindrical pulverized coal fluid injected from the pulverized coal injection nozzle and the oxygen gas nozzle. In which the intersection between the injection axis core wires, having a particular characteristic than the inner surface tip position of the tuyere provided in the front tip of the pulverized coal burner is adjusted so as to be located inwardly of the furnace is there.
[0015]
The pulverized coal blowing burner according to claim 2 is the pulverized coal blowing burner according to claim 1, wherein a plurality of the oxygen gas nozzles are arranged side by side on a concentric circle outside the pulverized coal blowing nozzle. A plurality of tuyere tip temperature adjusting gas nozzles are arranged side by side on a concentric circle outside the oxygen gas nozzle.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described with reference to the drawings.
[0019]
1-3 is a figure explaining the structural example of the pulverized coal injection nozzle of this invention.
[0020]
FIG. 1 is a view showing a longitudinal section on the base side of an example of the pulverized coal blowing burner of the present invention.
[0021]
In FIG. 1, the furnace observation tube 1, the pulverized coal tube 2, the tuyere tip temperature control gas tube 3, the oxygen gas tube 4 and the cooling water tube 5 on the right end side all extend to the nozzle portion on the burner tip side. The outer periphery of the pulverized coal blowing burner 6 has a water cooling structure, and the cooling water inlet 7 and outlet 8, the pulverized coal supply port 9, the tuyere tip temperature adjustment gas supply port 10, and the oxygen gas supply port 11 are provided at the base. Is provided. At the base of the in-furnace observation tube 1, ancillary facilities such as a purge gas inlet 12 for removing the deposits on the tip of the in-furnace observation tube are provided. For example, air is used as the purge gas.
[0022]
FIG. 2 is an enlarged longitudinal sectional view of the nozzle portion on the other end side, that is, the tip end side of the base portion of the pulverized coal blowing burner of the present invention shown in FIG.
[0023]
In FIG. 2, an in-furnace observation tube 1 is provided at the center of the burner axis, and a pulverized coal injection nozzle 2 is provided concentrically around the axis of the burner. The tuyere tip temperature adjusting gas nozzle 3 and the oxygen gas nozzle 4 are sequentially provided.
[0024]
In each nozzle configuration, the pulverized coal injection nozzle 2 is an annular slit nozzle, whereas the tuyere tip temperature adjustment gas nozzle 3 and the oxygen gas nozzle 4 are perforated nozzles, that is, a plurality of nozzle holes are concentrically arranged. Is arranged. The cross sectional shape of the gas nozzles 3 and 4 is preferably circular with a predetermined diameter. If it is circular, the manufacturing accuracy can be easily maintained at a high level. FIG. 3 is an AA arrow view of the portion of the pulverized coal blowing burner of FIG. 2 and corresponds to a front view of the burner portion.
[0025]
The shape and size of each nozzle 2, 3, 4 tip is determined appropriately for the flow rate of pulverized coal, tuyere tip temperature control gas and oxygen gas, and the linear velocity at the nozzle tip, and the injection of each fluid. Design according to the direction. Here, the ejection direction of each fluid is an important matter in the present invention and is as follows.
[0026]
FIG. 4 is a diagram illustrating directions in which each fluid is ejected from each nozzle. The pulverized coal fluid 2a blown from the pulverized coal blowing nozzle 2 proceeds in a cylindrical form with the axial line L of the pulverized coal blowing burner 6 as the axis, but the furnace does not collide with the inner surface of the tuyere 15 Turn inside.
[0027]
The axial line 4a of the oxygen gas jet injected from the oxygen gas nozzle 4 is inclined in the direction of the axial line L of the burner 6, and intersects the pulverized coal fluid 2a at the point Q. Pulverized coal and oxygen gas are mixed in a region centered on the point Q. The position of the point Q is located inside the furnace from the inner surface tip P of the tuyere 15.
[0028]
The tuyere tip temperature adjustment gas is used to adjust the tuyere tip temperature because pure oxygen gas is used as the combustion supporting gas of pulverized coal. This is necessary when the concentration is about 30% or more. Then, the tuyere tip temperature adjusting gas fluid 3a sprayed from the tuyere tip temperature adjusting nozzle 3 is directed to the raceway in the case of a furnace interior space at the tip of the tuyere, or a blast furnace.
[0029]
At this time, the injection direction of the tuyere tip temperature adjustment gas fluid 3a should not be directed to the direction of the mixing region of pulverized coal and oxygen gas. This is because pulverized coal is mixed with oxygen gas at a concentration as high as possible to enhance combustibility.
[0030]
The carrier gas for injecting pulverized coal is preferably oxygen gas. However, since oxygen gas is troublesome to handle, it is preferable to use air, oxygen-enriched air, CO ₂ gas, or the like. In addition, as the tuyere tip temperature adjusting gas, steam, blast furnace gas, coke oven gas, N ₂ gas, CO ₂ gas, and other gases that cause endothermic decomposition reaction of the gas, In the case of a blast furnace, any one that does not adversely affect the reduction of iron ore may be used.
[0031]
The reason why the pulverized coal injection nozzle is a circular slit nozzle is that when a large number of nozzle holes are provided on the concentric circle of the burner shaft core, nozzle clogging with pulverized coal tends to occur, and a large amount of pulverized coal This is because blowing is possible. Further, when the mixed fluid of pulverized coal and oxygen gas collides with the inner surface of the tuyere, the inner surface of the tuyere is significantly worn by the unburned pulverized coal in the mixed fluid, and the life of the tuyere is significantly reduced. Furthermore, if the ash in the pulverized coal melts and adheres to and accumulates on the inner surface of the tuyere due to the combustion of the mixed fluid, the life of the tuyere is significantly reduced, and the productivity of the blast furnace is reduced in addition to cost.
[0032]
The reason why the tuyere tip temperature adjusting gas nozzle 3 and the oxygen gas nozzle 4 are perforated nozzles is that they are easy to process and can be blown uniformly. In addition, it is good also as a circular pipe instead of a perforated nozzle, and in this case, the flow rate control for each hole becomes possible.
[0033]
FIG. 5 is an enlarged vertical cross-sectional view of a nozzle portion of another example of the pulverized coal blowing burner of the present invention and a tuyere portion continuously provided therewith. A pulverized coal injection nozzle 2 consisting of slit nozzles is provided concentrically outside the in-furnace observation hole 1 ′ provided in the central part of the axial center line of the burner, and a plurality of oxygen gas nozzles 4 (perforated nozzles) are provided outside the concentric circle. ) And a plurality of tuyere tip temperature control gas nozzles 3 (perforated nozzles) arranged concentrically outside thereof.
[0034]
In this case, the same performance as the pulverized coal blowing burner shown in FIGS. And about the design of each nozzle hole, it is desirable to adjust those shapes and dimensions, and the injection direction of each fluid similarly to the case of FIGS.
[0035]
In addition, when a gas that condenses as the temperature decreases, such as water vapor, is used as the tuyere tip temperature adjustment gas, this accumulates in the lower region of the tuyere near the water-cooled pipe, and pulverized coal accumulates and the tuyere The mouth is closed. In order to prevent this, it is necessary to shake off the condensed liquid with another gas so that the liquid is not accumulated in the tuyere.
[0036]
Therefore, in the case where the condensable gas is used as the tuyere tip temperature adjusting gas, the condensed liquid is removed from the tuyere tip by providing the oxygen gas nozzle below the position of the tuyere tip temperature regulating gas nozzle. Is effective. That is, for example, in FIG. 3, the problem is solved when the oxygen gas nozzle 40 is located below the tuyere tip temperature adjusting gas nozzle 30. Therefore, it is necessary that the oxygen gas nozzle 4 is on the outer peripheral side of the burner than the tuyere tip temperature adjusting gas nozzle 3.
[0037]
【The invention's effect】
As described above, according to the present invention, pulverized coal can be efficiently burned as an inexpensive fuel or reducing agent in a blast furnace or other wide-ranging industrial reactor or industrial reactor, or industrial heating furnace. This is an industrially useful effect that can be achieved.
[Brief description of the drawings]
FIG. 1 is a view showing a longitudinal section on the base side of an example of a pulverized coal blowing burner according to the present invention.
FIG. 2 is an enlarged vertical cross-sectional view of a nozzle portion at a tip portion which is the other end side of the base portion of the pulverized coal blowing burner of FIG. 1 and a tuyere portion provided continuously therewith.
FIG. 3 is a view taken along the line AA of the portion of the pulverized coal blowing burner of FIG. 2;
FIG. 4 is a view for explaining the injection direction of each fluid from a nozzle in an example of a pulverized coal blowing burner according to the present invention.
FIG. 5 is an enlarged longitudinal sectional view of a nozzle portion of another example of the pulverized coal blowing burner according to the present invention and a tuyere portion continuously provided therewith.
[Explanation of symbols]
1: In-furnace observation tube 1 ′: Furnace observation hole 2: Pulverized coal tube 2a: Fluid of pulverized coal 3: Tuyere tip temperature adjustment gas tube 3a: Tuyere tip temperature adjustment gas fluid 4: Oxygen gas tube 4a: Oxygen gas jet Axis line 5: cooling water pipes 6, 6 ': pulverized coal blowing burner 7: cooling water inlet 8: cooling water discharge port 9: pulverized coal supply port 10: tuyere tip temperature adjustment gas supply port 11: oxygen gas supply port 12 : Air inlet 13: gate valve 14: viewing window 15: tuyere 30: tuyere tip temperature adjustment gas nozzle 40: oxygen gas nozzle L: axis line P of pulverized coal blowing burner Q: tip Q of tuyere inner surface Q: pulverized coal fluid Position where the axis of the oxygen gas jet intersects

Claims (2)

An in-furnace observation hole is provided in the central portion including the axial line of the burner, and a slit-shaped pulverized coal injection nozzle for injecting pulverized coal is provided concentrically outside the in-furnace observation hole. A plurality of tuyere tip temperature adjusting gas nozzles for injecting gas for adjusting the temperature of the furnace tuyere tip are arranged side by side on a concentric circle outside the blowing nozzle, and concentric circles outside the tuyere tip temperature regulating gas nozzle are provided. A plurality of oxygen gas nozzles for ejecting oxygen gas are provided side by side , at least one of the tuyere tip temperature adjustment gas nozzle and the oxygen gas nozzle is formed of a circular pipe, and the pulverized coal injection nozzle and the The oxygen gas nozzle is such that the intersection of the injection direction of the cylindrical pulverized coal fluid injected from the pulverized coal injection nozzle and the axial line of the oxygen gas injection direction is the pulverized powder. Pulverized coal blown burner, characterized in that from the inner surface the tip position of the tuyere provided in the front tip of the burner is adjusted so as to be located inwardly of the furnace. A plurality of the oxygen gas nozzles are arranged side by side on a concentric circle outside the pulverized coal blowing nozzle, and a plurality of the tuyere tip temperature adjusting gas nozzles are arranged on a concentric circle outside the oxygen gas nozzle. The pulverized coal blowing burner according to claim 1, characterized in that:

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