JPS6053082B2 - Method of injecting powdered fuel into a blast furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of injecting powdered fuel, which is generally considered to have poor flammability, in a state of good combustibility. Specifically, as the flammability improves, This invention relates to a method of blowing in an optimal state while avoiding as much as possible the adhesion of ash (deposition on the inner surface of the blow pipe), which tends to occur simultaneously.

As for the fuel injected in blast furnace operations, due to the effects of soaring oil prices, heavy oil injection alone has faded, and all-coke operation has become the mainstream.

However, in order to alleviate the difficulty of all-coke operation and save on expensive coke, pulverized fuel injection is being considered or implemented. However, pulverized pulverized fuel (hereinafter collectively referred to as pulverized fuel in this specification) has the drawbacks of having a slower combustion rate than heavy oil and containing unresolved components such as ash, so it is difficult to inject it. In the meantime, it is necessary to take various measures. This will be explained more specifically as follows. In conventional heavy oil injection, the tip of the burner was placed near the boundary between the blast furnace outlet and the blow pipe, and the injected heavy oil was almost completely burned inside the outlet and in the raceway immediately after the tuyere. On the other hand,
If powdered fuel is injected from the same position, it will not be completely burned in the tuyere or raceway, resulting in a poor combustion rate. As a result of further study, we felt that if we had a blowing position, we could move it upstream and blow it into the blowpipe, and if we ignited and burned it in the blowpipe, we could considerably improve the combustion rate. On the other hand, powdered fuel contains a small amount of ash, although the difference is about l, and this ash melts due to the heat of combustion, but when this molten material collides with the inner surface of the blow pipe, it adheres to that part. This accumulation of ash not only narrows the air passage and makes it difficult to maintain stable injection of fuel, but also poses a risk of unstable injection of hot air from the tuyere.・The more the powdered fuel is injected into the upstream side, the more the accumulation becomes more serious.
Based on the above-mentioned knowledge, the present inventors conducted studies to clarify the cause of adhesion and accumulation of ash, and the following facts were confirmed.

In other words, the powdered fuel blown from the fuel injection burner (hereinafter simply referred to as the burner) comes out from the burner tip and comes into contact with the hot air flowing at high speed inside the blow vibe, forming a flame, as will be clarified in the examples below. However, the greater the degree of contact of this flame with the wall surface of the blow vibrator, the greater the adhesion and accumulation of ash. This is because when the wall of the blow vibrator is overheated by the flame, the ash in the powdered fuel, which is in a molten or semi-molten state in the flame, tends to adhere to the wall and gradually accumulates. it is conceivable that. Therefore, in order to prevent the accumulation of ash, it is considered effective to suppress the flame from coming into contact with the blow vibe inner wall as much as possible. The present invention was completed as a result of further research based on the above knowledge, and its configuration consists of a burner for blowing powdered fuel and a wall of a blow vibrator for blowing hot air connected to the blast furnace tuyere. A method for blowing powdered fuel into a blast furnace, in which the powdered fuel is penetrated and entered into the blow vibe, and the powdered fuel blown from the burner is blown from the blast furnace tuyeres together with the hot air flowing inside the blow vibe. If the center of the tip of the burner does not coincide with the axis of the blow vibe, the tip of the burner
Below 3, point A. ,B. , C is set at a position where the angle ZBAC in the triangle is 11 to 25 degrees, and the powdered fuel is injected.

1 Center A at the tip of the burner 2 Point C on the inner circumferential surface of the blow vibe outlet end closest to point B 3 B, the intersection of the perpendicular line from point A to the tip of the blow vibe and the outlet surface of the Bunilow pipe. The effects will be explained in detail.

Figure 1 is a schematic diagram of the apparatus used in the combustion experiment, which is designed to resemble an actual blast furnace tuyere. Powdered fuel A is conveyed from an above-ground hopper 1 to a coal pin 3 by a screw conveyor 2. A powdered fuel quantitative feeder 4 is provided at the bottom of the coal pin 3, and the powdered fuel A cut out in fixed amounts at this portion 4 is sent to the burner 7 through a transportation pipe 6 together with transportation air 5. . On the other hand, the hot air obtained from the high-temperature hot air stove 8 is transferred from the blow pipe 9 to the blow vibrator 10.
and is sent to the combustion test furnace 12 via the water-cooled tuyeres 11. 13 in the figure is a chimney. The combustion blowing section of a blast furnace is completely different from general combustion equipment, with 10 blow vibes, 11 water-cooled tuyeres, and 11 blow vibes.
This experimental apparatus approximates an actual blast furnace injection section, and its structure is shown in FIG. 2 as an enlarged view of the main part.

In addition, this test furnace is equipped with a number of observation windows to observe the combustion and ignition conditions of the powdered fuel, as well as to measure the temperature inside the furnace, the gas composition inside the furnace, the dust inside the furnace, the amount of flame radiation, etc. In addition, a viewing window 14 is provided at the upstream curved portion of the blow vibe 10 for observing the state of adhesion of ash to the inner wall of the blow vibe 10. The conditions for the experiment described later using this device are as follows. Experimental conditions Powdered fuel: Volatile content 25-45% Powdered fuel injection amount: 100k9/hour Same injection speed: 10-25Nm/sec Transportation fuel air-solid ratio: 5-25k9/K9 Hot air temperature: 1200℃ Same Air ratio: 2.0 Same pressure: 2000 rnmAg Same Tuyere tip flow rate: 250 TrL/sec Blow vibe inner diameter: 0.13 to 0.20 mφ In this device and conditions, first, the flame when the burner 6 tip position in the blow vibe 10 is changed variously. The relationship between the formation status and the amount of ash deposited was conceptually confirmed.

As a result, for example, as shown in FIG. 3 (conceptual diagram), when the tip position of the burner 6 is aligned with the axis 10-P of the blow vibe 10, the flame F is moved from the axis 10-P to the blow vibe 10. Since the ash spreads evenly toward the inner wall side, adhesion and accumulation of ash can be prevented by adjusting the distance Z from the tip of the burner 6 to the opening end of the blow vibe, the inner diameter D of the blow vibe 10, etc. However, as shown in FIGS. 4 and 5, if the tip of the burner 6 and the axis 10-P do not match, the flame F is biased toward the wall closest to the blow vibe 6, and molten ash x adheres to this area. This was confirmed.

Therefore, it is necessary to set the powder fuel injection position so that ash will not adhere to the blow vibe inner wall even if the flame F is lopsided as described above. Therefore, as shown in FIG. 6, the points B1 and 3B are the intersections of the perpendicular S from the tip center point Al2A of burner 6 to the tip of the blow vibe 10 and the blow vibe outlet surface (boundary surface with the water-cooled tuyere 11). Assuming a virtual triangle N phantom formed by one point C1 on the inner circumferential surface of the blow vibrator outlet end closest to it, we investigated the effects on the combustion rate and the amount of ash accumulation when the angle ZBAC (i.e., θ) was variously changed.

However, the combustion rate refers to the total combustion rate calculated from the amount of CO2 in the gas collected in the combustion furnace 0.20 m downstream from the tip of the tuyere. The results are shown in FIG. 7, and as the angle 0 becomes smaller, the adhesion and accumulation of ash becomes more significant, and when θ becomes 11 degrees or more, almost no ash adhesion is observed.

However, as the angle θ increases, it means that the distance L from the burner tip to the blow-vibrator outlet end (Figure 3) decreases, and as the combustion zone becomes shorter, the combustion rate decreases. . In particular, if the angle θ exceeds 40 degrees, the combustion rate will decrease significantly, so the angle θ should be set to 40 degrees or less. Among them, the most preferable angle is 0,
As is clear from FIG. 7, the angle is in the range of 11 to 25 degrees.
Note that the above angle 0 varies depending on the inner diameter D1 of the blow vibe 10, the distance L1 from the burner tip to the blow vibe opening end, and the distance 1 (FIG. 6) between the burner tip and the wall closest to the blow vibe. The distances L and l may be adjusted appropriately according to the inner diameter D of the vibrator 10 so that the angle θ falls within the preferable range. The present invention is roughly constructed as described above, and by appropriately adjusting the tip position of the burner for blowing powdered fuel in consideration of the relationship with the angle θ, problems caused by adhesion and accumulation of ash can be prevented. It became possible to increase the combustion rate of powdered fuel without causing any problems.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the combustion experiment equipment, Fig. 2 is an enlarged view of the main part of the powder fuel injection part in the equipment, and Figs. 3 to 5 are explanatory diagrams showing the relationship between the fuel injection position and flame and ash adhesion. FIG. 6 is a conceptual diagram for explaining the basis for setting the angle 0 in the present invention,
FIG. 7 is a graph showing the relationship between the angle θ, the combustion rate, and the presence or absence of ash adhesion. 1: Ground hopper, 2: Screw conveyor, J7: Powdered fuel injection burner, 10: Plow pipe, 11: Water-cooled tuyere, 12: Combustion furnace.

Claims (1)

[Scope of Claims] 1. A burner for blowing powdered fuel is passed through the wall of a blow pipe for blowing hot air connected to a blast furnace tuyere and thrust into the blow pipe, and the powder blown from the burner is A powder fuel blast furnace injection method in which fuel is injected from a blast furnace tuyere together with hot air flowing in a blow pipe, and when the center of the tip of the burner does not coincide with the axis of the blow pipe, the tip of the burner is A method for injecting powdered fuel into a blast furnace, characterized in that the powdered fuel is injected at a position where the angle BAC in the triangle formed by the following three points A, B, and C is 11 to 25 degrees. (1) Center A of the tip of the burner (2) Intersection B between the perpendicular line from point A to the tip of the blowpipe and the blowpipe outlet surface (3) Point C on the inner peripheral surface of the blowpipe outlet end closest to point B