JP4127032B2 - Blast furnace pulverized coal injection burner and pulverized coal injection method into blast furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to pulverized coal injection burner and pulverized coal injection method into the blast furnace using the same for injecting pulverized coal into the furnace through the Oite tuyeres into the blast furnace.
[0002]
[Prior art]
In blast furnace operation, it is common to inject pulverized coal as an alternative fuel for coke, and recently there is an example in which an operation exceeding a pulverized coal ratio of 260 kg per ton of pig iron is performed (for example, see Non-Patent Document 1). .
However, there is a possibility that further reduction of coke usage will be required in the future due to circumstances such as the future supply and demand of coke, aging of coke ovens, and suppression of carbon dioxide generation, It is considered necessary to perform pulverized coal injection.
[0003]
[Non-Patent Document 1]
“Materials and Processes Vol.11 (1998)” p834
[0004]
In general, pulverized coal is blown into the blast furnace together with hot air through a pulverized coal blowing burner inserted through a blow pipe attached to a tuyere. In this case, it is desirable to blow pulverized coal uniformly from all tuyere so that the gas flow and temperature distribution are uniform in the blast furnace circumferential direction.
However, when pulverized coal is blown into the blast furnace with a pulverized coal blowing burner, foreign matter adheres and grows on the tip of the burner, resulting in clogging of the burner, and pulverized coal is uniformly blown from all tuyere in the blast furnace circumferential direction. There is a problem that it becomes impossible.
[0005]
In FIG. 9, the structure of the front-end | tip part of a conventional pulverized coal blowing burner and the adhesion state of a foreign material are shown. Generally, a conventional pulverized coal blowing burner has a double pipe structure composed of an inner pipe 7 (pulverized coal blowing pipe) and an outer pipe 8, and pulverized coal is blown from the inner pipe 7 by a carrier gas, and the outer pipe 8. A cooling fluid such as air flows through the flow path 9 between the inner pipe 7 and the inner pipe 7. When such a pulverized coal blowing burner is used, foreign matters such as volatile matter released from the heated pulverized coal and molten ash generated by the combustion of the pulverized coal adhere to the tip of the inner tube 7, and this gradually increases. Grows and burner clogging occurs. If the burner is clogged with such foreign matter, the amount of pulverized coal blown in the blast furnace circumferential direction will be uneven and the heat balance in the blast furnace circumferential direction will be disrupted, causing serious problems in blast furnace operation. Become.
[0006]
To prevent such foreign matter adhesion, the inner surface of the inner cylinder (inner tube) at the tip of the burner is tapered outward to suppress the generation of vortex at the tip of the burner and There is a technology that prevents the formation of deposits at the tip of the inner tube by increasing the difference in length of the tube (outer tube) and reducing the retention of air flow at the step portion between the outer tube and the inner tube. It has been proposed (see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-6-158126
[Problems to be solved by the invention]
However, when the amount of pulverized coal blowing increases, even the pulverized coal blowing burner disclosed in Patent Document 1 cannot sufficiently suppress foreign matter adhesion.
In recent years, with the increase in the amount of pulverized coal injection, (1) ash generated during combustion of pulverized coal adheres to the tuyere, making the blast furnace air flow unstable. (2) In the tuyere and blowpipe Since the gas temperature and volume increase due to the combustion of pulverized coal, the blowing pressure rises and its fluctuation increases, and problems such as making the blowing of the blast furnace unstable are becoming apparent. In order to avoid such problems, it is effective to place the pulverized coal injection position by the pulverized coal injection burner as close to the inside of the furnace (tip of the tuyere) as possible. For this reason, in recent blast furnace operations, the tip of the tuyere The distance between the position and the tip position of the pulverized coal blowing burner is set to be very small (for example, about 50 to 100 mm).
[0009]
However, it has been found that when the pulverized coal blowing burner disclosed in Patent Document 1 is used in such an arrangement, the tip of the burner is easily damaged by radiant heat from the blast furnace combustion zone. This is considered to be due to a decrease in the cooling effect of the inner cylinder because the difference in length between the inner cylinder and the outer cylinder was increased.
[0010]
Accordingly, the object of the present invention is to effectively suppress the adhesion of foreign matter at the burner tip, and properly cool the burner tip even if the distance between the burner tip position and the tuyere tip position is reduced. It is to provide a blast furnace pulverized coal blowing burner that can be maintained.
Another object of the present invention is to provide a method for blowing pulverized coal into a blast furnace using such a pulverized coal blowing burner.
[0011]
[Means for Solving the Problems]
The features of the present invention for solving such problems are as follows.
[1] In the blast furnace pulverized coal blown burner for injecting pulverized coal into the blast furnace through the tuyere,
The tip side portion of the pulverized coal blowing pipe constituting the burner main body is a reduced diameter pipe portion whose inner diameter is gradually reduced toward the pipe end side, and a pipe end portion connected to the reduced diameter pipe portion, the inner diameter of the pipe A blast furnace pulverized coal-injection burner characterized by comprising a diameter-expanded pipe portion that gradually increases in diameter toward the end side.
[2] A pulverized coal blowing burner for blast furnace , wherein the pulverized coal blowing burner of [1] has an equal-diameter pipe portion having a constant inner diameter between the reduced diameter pipe portion and the enlarged diameter pipe portion.
[3] A pulverized coal-injection burner for a blast furnace according to the above [1] or [2], wherein the divergence angle θ with respect to the tube axis of the inner surface of the expanded diameter tube portion is 10 ° or more.
[0012]
[4] The pulverized coal blowing burner according to any one of [1] to [3] above, wherein the burner body has a double-pipe structure composed of an inner tube and an outer tube, and the inner tube constitutes a pulverized coal blowing tube And a pulverized coal-injection burner for a blast furnace , wherein a passage for cooling fluid is formed between the outer tube and the inner tube.
[5] The pulverized coal blowing burner according to any one of the above [1] to [3], wherein the pulverized coal blowing tube has a single-tube structure having a flow path for cooling fluid inside the tube wall. Blast furnace for blast furnace .
[6] The pulverized coal for blast furnace according to any one of the above [1] to [5], wherein the tube portion on the rear end side of the burner connected to the reduced diameter tube portion is an equal diameter tube portion. Blow burner.
[7] A method for blowing pulverized coal into a blast furnace using the pulverized coal blowing burner according to any one of [1] to [6] above,
It is characterized in that the tip side portion of the burner body of the pulverized coal blowing burner is inserted into a blast furnace tuyere or a blow pipe connected thereto, and pulverized coal is blown from the pulverized coal blowing burner into the blast furnace through the tuyere. To pulverize coal into the blast furnace .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an embodiment of the pulverized coal blowing burner of the present invention. FIG. 1 is a longitudinal sectional view of the pulverized coal blowing burner. FIG. 2 is a blast furnace to which the pulverized coal blowing burner A of the present invention is attached. It is a longitudinal cross-sectional view of a tuyere part.
In FIG. 1, reference numeral 1 denotes a burner body having a double-pipe structure. The burner body 1 is composed of an inner tube of a pulverized coal blowing tube 2 and an outer tube 3, and these pulverized coal blowing tube 2 (inner tube) and an outer tube. Between the pipes 3 constitutes a flow path 4 for cooling fluid. The tips of the pulverized coal blowing pipe 2 and the outer pipe 3 are open, and both pipe ends are at substantially the same position in the longitudinal direction of the burner body. A cooling fluid inlet 30 is provided at the rear end of the outer tube 3. The tip of the burner is easily melted by the heat generated by the combustion of pulverized coal and the radiant heat from the red coke in the raceway. By adopting the structure (cooling structure) provided with the flow path 4 for the cooling fluid as described above, In addition, it is possible to effectively suppress melting of the burner tip.
[0014]
The tip portion of the pulverized coal blowing tube 2 is a reduced diameter pipe portion 20 whose inner diameter is gradually reduced toward the pipe end side, and a pipe end portion connected to the reduced diameter pipe portion 20, and the inner diameter is the pipe end. It is comprised from the diameter-expanded pipe part 21 (short pipe part) gradually diameter-expanded toward the side. Therefore, the inner diameter D ₁ of the end portion near the burner rear end of the reduced diameter tube portion 20 (= the end portion of the equal diameter tube portion 22 closer to the burner rear end side than the reduced diameter tube portion 20), and the reduced diameter tube portion 20 end of the burner tip closer to the inner diameter D ₂ of the (= burners near the rear end of the end portion of the radially enlarged tube part 21), the inner diameter D ₃ of the tip portion of the radially enlarged tube portion 21 (= the tube end), D _1> The relationship of D ₂ , D ₃ > D ₂ is satisfied. In addition, although the inner diameter of the diameter-reduced tube portion 20 and the diameter-expanded tube portion 21 of the present embodiment is both tapered, these inner surfaces are not necessarily tapered, for example, in the tube axis direction. It may be configured in an arc shape or include an arc-shaped portion, or may be a combination of a plurality of tapered surfaces having different taper angles in the tube axis direction.
[0015]
2, 5 is a tuyere, 6 is a blow pipe for blowing hot air connected to the tuyere 5, and the pulverized coal blowing burner A shown in FIG. However, the tip side portion is disposed so as to be located in the tip side portion or tuyere 5 of the blow pipe 6.
In the pulverized coal blowing burner A as described above, pulverized coal accompanying the carrier gas is introduced into the pulverized coal blowing tube 2, and this pulverized coal enters the tuyere 5 or the blow pipe 6 from the tip of the pulverized coal blowing tube 2. It is blown and introduced into the furnace while burning. A cooling fluid such as air is supplied to the flow path 4 between the pulverized coal blowing pipe 2 (inner pipe) and the outer pipe 3, and the tip of the pulverized coal blowing burner (in particular, the tip of the pulverized coal blowing pipe 2). Part) is cooled.
[0016]
The principle of the foreign matter adhesion preventing action of the pulverized coal blowing burner A of the present invention will be described based on FIGS. 3 (a) and 3 (b).
3A schematically shows the flow x of the carrier gas (the carrier gas of the pulverized coal) in the tip side portion of the pulverized coal blowing tube 2, and FIG. 3B schematically shows the flow y of the pulverized coal. It is shown. According to this, the flow x of the carrier gas basically follows the inner space of the reduced diameter pipe part 20 and the enlarged diameter pipe part 21 connected thereto. That is, the flow x of the carrier gas is once throttled by the reduced diameter pipe portion 20, but when it reaches the enlarged diameter pipe portion 21, it expands along the enlarged inner diameter. On the other hand, since the pulverized coal that is solid has a larger inertia than the carrier gas, the flow is restricted by the reduced diameter pipe portion 20, so that even if it reaches the enlarged diameter pipe portion 21, the tube axis (burner central axis) ) The flow y is concentrated on the side.
[0017]
As described above, the adhering foreign matter at the tip of the burner is caused by adhesion of volatile matter released by the temperature rise of the pulverized coal or molten ash produced by the combustion of the pulverized coal. FIG. As shown in the figure, the pulverized coal is concentrated in the pipe axis side even if it reaches the diameter-expanded pipe part 21 by being squeezed by the diameter-reduced pipe part 20, and the diameter-expanded pipe part that is the pipe end part Since a sufficient distance is provided between the flow of the pulverized coal and the pipe in 21, it is possible to effectively suppress the volatile matter and molten ash from adhering to the pipe end. Here, the pulverized coal blowing burner of Patent Document 1 described above is provided with a taper on the inner surface of the inner pipe (pulverized coal blowing pipe), but has a reduced diameter pipe portion as in the present invention on the upstream side thereof. Therefore, the flow of pulverized coal is not concentrated on the tube shaft side as shown in FIG. For this reason, the distance between the flow of the pulverized coal and the pipe end of the inner cylinder cannot be sufficiently secured, and as a result, the adhesion of foreign matter at the pipe end cannot be prevented appropriately.
[0018]
Next, a preferable structure of the pulverized coal blowing burner of the present invention will be described.
First, it is preferable that a spread angle θ (an angle formed by an extension surface of the inner surface of the enlarged tube portion 21 and the tube axis) with respect to the tube axis of the inner surface of the enlarged tube portion 21 is 10 ° or more. The effect of preventing foreign matter from adhering to the tip of the burner is obtained to some extent even when the spread angle θ is less than 10 °. However, when the spread angle θ is 10 ° or more, a particularly remarkable effect of preventing foreign matter is obtained.
[0019]
In order to confirm the optimum range of the spread angle θ of the inner surface of the expanded diameter pipe portion 21, in the blast furnace (inner volume 3223 m ³ ) having 34 tuyere in the circumferential direction, various expansion angles θ of the inner surface of the expanded diameter tube portion are different. The pulverized coal blowing operation was performed using a pulverized coal blowing burner, and the adhesion of foreign matter to the burner tip and the durability (life) of the burner were evaluated. In this test operation, a pulverized coal-injection burner having the same spread angle θ on the inner surface of the expanded pipe portion was applied to all tuyere of the blast furnace. For comparison, the same evaluation was performed on a conventional pulverized coal-burning burner as shown in FIG. Note that the inner diameter D ₂ and the inner surface taper angle of the reduced tube portion 20 shown in FIG. 1, was fixed to the extent that does not significantly change the pulverized coal hopper pressure. The blast furnace operating conditions during each test period were almost constant, and the test period was one year.
[0020]
FIG. 4 shows the relationship between the spread angle θ of the inner surface of the enlarged diameter pipe portion and the number of tuyere where foreign matter adhesion (foreign matter adhesion that closes the burner tip portion) occurs in the test tube operation. . According to the figure, even if the spread angle θ is about 2 °, the effect of preventing the adhesion of foreign matter is recognized as compared with the conventional burner, but the adhesion of foreign matter is remarkably reduced especially when the spread angle θ is 10 ° or more. I understand.
[0021]
FIG. 5 shows the relationship between the spread angle θ of the inner surface of the expanded pipe portion and the burner life in the test operation. Here, the burner life refers to the period from the start of use until the melting point of the burner becomes noticeable and replacement is required. According to FIG. 5, it can be seen that the burner life is almost constant regardless of the spread angle θ of the inner surface of the expanded pipe portion. This is probably because the pulverized coal blowing burner of the present invention was not cooled much as the length of the inner tube and the outer tube was different from the pulverized coal blowing burner of Patent Document 1, so that it was cooled efficiently.
[0022]
The upper limit is not particularly spread angle theta, the diameter of the distal end portion of the radially enlarged tube portion 21 in order to secure the length L ₁ of the radially enlarged tube part 21 the divergence angle theta is the too large increases, the outer tube 3 In order to avoid such a problem, the spread angle θ is preferably about 50 ° as an upper limit.
There is no particular restriction on the length L ₁ of the radially enlarged tube part 21, the too short relative to the diameter of the inner tube 2, the effect is sufficiently obtained in the present invention by the provision of the enlarged tube part 21 On the other hand, if the length is too long, the structural connection with the outer tube 3 becomes a problem. Therefore, 0.1D ₁ ≦ L in relation to the inner diameter D ₁ of the reduced diameter tube portion 20 near the rear end of the burner. It is preferable that the length satisfies ₁ ≦ D ₁ .
[0023]
Further, the degree of diameter reduction of the reduced diameter pipe portion 20, that is, the ratio D ₂ / D ₁ of the inner diameter D _{2 of the} end portion near the burner tip of the reduced diameter tube portion 20 and the inner diameter D _{1 of the} end portion near the burner rear end. Although there is no special limitation, if this ratio is too large, the effect of the present invention is reduced. On the other hand, if it is too small, there is a possibility that the blowing of pulverized coal may be hindered, so 0.5 ≦ D ₂ / D ₁ It is preferable to be about ≦ 0.9.
[0024]
The pulverized coal blowing burner of the present invention may have a structure having an equal-diameter pipe portion 23 having a constant inner diameter between the reduced-diameter pipe portion 20 and the enlarged-diameter pipe portion 21 as shown in FIG.
Further, in the pulverized coal blowing burner of the present invention, the inner surface of the pulverized coal blowing tube 2 only needs to satisfy the above-described conditions. Therefore, as shown in FIG. 7, the outer surface of the pulverized coal blowing tube 2 has a straight shape. Also good. Thereby, the cross-sectional area of the flow path 4 can be made constant in the burner longitudinal direction.
[0025]
Further, when the burner body has a double pipe structure composed of an inner pipe and an outer pipe as in the present embodiment, the pulverized coal blowing pipe 2 is appropriately cooled by the cooling fluid supplied from the outer pipe 3. You may make a difference in the length of the inner pipe (pulverized coal blowing pipe 2) and the outer pipe 3 as shown in FIG.
Further, in the burner of the present invention, the pulverized coal blowing pipe 2 can be made into a single pipe structure provided with a flow path for cooling fluid inside the pipe wall without providing the outer pipe 3 as in the above embodiment. FIG. 8 shows one embodiment, and a cooling fluid channel 4a is provided inside the tube wall of the pulverized coal blowing tube 2, and a cooling fluid such as cooling water supplied into the channel 4a. As a result, the pulverized coal blowing pipe 2 is cooled. The flow path 4a is provided with a supply part (not shown) for supplying a cooling fluid from outside the pipe and a discharge part (not shown) for discharging the cooling fluid that has flowed through the flow path 4a to the outside of the pipe. et al are.
[0026]
【The invention's effect】
As described above, the pulverized coal blowing burner of the present invention can effectively suppress foreign matter adhesion at the burner tip. In addition, when the burner body has a double-pipe structure, foreign matter adhesion at the burner tip can be effectively suppressed without causing the pulverized coal blowing tube to protrude from the outer tube, so the burner tip position and tuyere tip Even if the distance from the position is reduced, the cooling of the burner tip can be properly maintained. For this reason, the distance between the tip position of the burner and the tip position of the tuyere can be made sufficiently small to stabilize the blowing of the blast furnace .
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an embodiment of the pulverized coal blowing burner of the present invention. FIG. 2 is a longitudinal sectional view of a blast furnace tuyere portion to which the pulverized coal blowing burner of FIG. 1 is attached. FIG. 4 is an explanatory view showing the principle of the foreign matter adhesion preventing action by the charcoal blowing burner. FIG. 5 is a graph showing the relationship between the spread angle θ of the inner surface of the expanded pipe portion and the burner life in the pulverized coal blowing burner of the present invention. FIG. 6 is another embodiment of the pulverized coal blowing burner of the present invention. Fig. 7 is a longitudinal sectional view of the tip portion of the pulverized coal blowing pipe in Fig. 7. Fig. 8 is a longitudinal sectional view of the tip portion of the pulverized coal blowing pipe in another embodiment of the present invention. Fig. 9 is a longitudinal sectional view of the tip of the pulverized coal blowing pipe in another embodiment. Fig. 9 is an explanatory view showing the longitudinal section of the tip of the conventional pulverized coal blowing burner and the state of foreign matter adhesion.
DESCRIPTION OF SYMBOLS 1 ... Burner main body, 2 ... Pulverized coal blowing pipe, 3 ... Outer pipe, 4, 4a ... Flow path, 5 ... Tuyere, 6 ... Blow pipe, 20 ... Reduced diameter pipe part, 21 ... Expanded pipe part, 22, 23 ... isometric pipe part, A ... pulverized coal blowing burner

Claims (7)

In blast furnace pulverized coal blown burner for injecting pulverized coal into the blast furnace through the tuyere,
The tip side portion of the pulverized coal blowing pipe constituting the burner main body is a reduced diameter pipe portion whose inner diameter is gradually reduced toward the pipe end side, and a pipe end portion connected to the reduced diameter pipe portion, the inner diameter of the pipe A blast furnace pulverized coal-injection burner characterized by comprising a diameter-expanded pipe portion that gradually increases in diameter toward the end side. 2. The blast furnace blast- coal-burning burner according to claim 1, further comprising an equal-diameter tube portion having a constant inner diameter between the reduced-diameter tube portion and the expanded-diameter tube portion. The blast furnace- blown coal burner for blast furnace according to claim 1 or 2, wherein a divergence angle θ with respect to the tube axis of the inner surface of the expanded diameter pipe portion is 10 ° or more. The burner body has a double pipe structure consisting of an inner pipe and an outer pipe, the inner pipe constitutes a pulverized coal blowing pipe, and the flow path for cooling fluid is constituted between the outer pipe and the inner pipe A pulverized coal-injection burner for a blast furnace according to any one of claims 1 to 3. The pulverized coal blowing burner for a blast furnace according to any one of claims 1 to 3, wherein the pulverized coal blowing tube has a single pipe structure provided with a flow path for cooling fluid inside the tube wall. The pulverized coal-injection burner for blast furnace according to any one of claims 1 to 5, wherein the tube portion on the rear end side of the burner where the reduced-diameter tube portions are connected is an equal-diameter tube portion. A method for blowing pulverized coal into a blast furnace using the pulverized coal blowing burner according to claim 1,
It is characterized in that the tip side portion of the burner body of the pulverized coal blowing burner is inserted into a blast furnace tuyere or a blow pipe connected thereto, and pulverized coal is blown from the pulverized coal blowing burner into the blast furnace through the tuyere. To pulverize coal into the blast furnace .

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