JPS6053081B2 - Method of injecting powdered fuel into 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. This invention relates to a method of blowing in an optimal state while avoiding as much as possible the accompanying ash adhesion (deposition on the inner surface of the blow pipe).

As for the injection fuel used in blast furnace operations, due to the effects of soaring oil prices, the injection of heavy oil 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, injection of pulverized fuel such as pulverized coal is being considered or implemented. However, pulverized coal and other pulverized fuels (hereinafter collectively referred to as pulverized fuels) have the drawbacks of having a slower combustion rate than heavy oil and containing unresolved components such as ash, so they are not suitable for injection. Therefore, 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 is placed near the boundary between the blast furnace tuyere and the blowpipe, and the injected heavy oil is almost completely burned inside the tuyere 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 within 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 to varying degrees, 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 and accumulates on that part. to narrow the ventilation passage,
Not only will it be difficult to maintain a stable injection of fuel, but there is also the danger that the injection of hot air from the tuyeres will become unstable. The more you move it to the side, the more noticeable it becomes.

Based on the above knowledge, the inventors of the present invention have conducted intensive research in order to establish a technology that can increase the combustion rate of powdered fuel to the same level as that of liquid fuel while preventing the adhesion and accumulation of ash. It's here.

The present invention was completed as a result of such research, and has a structure in which a burner for blowing powdered fuel is passed through the wall of a blow vibe for blowing hot air connected to a blast furnace tuyere and into the blow vibe. , the burner is thrust into the blast furnace so that the center of the tip thereof is near the axis of the vibrator, and the powdered fuel blown from the burner is blown into the blast furnace through the blast furnace tuyeres together with the hot air of 950° C. or higher flowing inside the blow vibrator. The gist of this powdered fuel injection method is that the tip of the burner is positioned 0.1 to 0.35 m upstream from the boundary between the blast furnace tuyere and the blow vibe. The configuration and effects of the present invention will be explained in detail below along with the progress of the experiment.

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 a fixed amount of the powdered fuel A is cut out from this portion and sent to the burner 7 through a transport pipe 6 together with transport air 5. On the other hand, high-temperature hot air stove 8
The hot air obtained is sent from the blast pipe 9 to the combustion test furnace 12 via the blow vibe 10 and the water-cooled tuyeres 11. 1 in the diagram
3 is the chimney. The fuel injection section of a blast furnace is completely different from a general combustion device and consists of a blow vibrator 10 and a water-cooled tuyere 11. Therefore, this experimental device was designed to approximate an actual blast furnace injection section, and the main parts are shown in Figure 2. The structure is shown in an enlarged view.

In addition, this test furnace is equipped with many observation windows to observe the combustion and ignition conditions of the powdered fuel.
Inspection holes for measuring the furnace gas composition, furnace dust, flame radiation amount, etc. are provided at the upstream bend of the blow vibe 10. A peephole 14 is provided for observing the adhesion of ash to the wall of the blow vibrator 10. The conditions for the series of experiments described later using this apparatus are as follows. Experimental conditions Powdered fuel: volatile content 20-45% by weight Powdered fuel injection amount: 100k9/hour Same injection speed: 10-25Nm/sec Transportation fuel solid-air ratio: 5-25k9/K9 Hot air temperature: 800-12000C Same pressure D2000mAq Tuyere tip flow rate: 2507T1,/sec (1200℃) Blow vibe diameter: 0.13 to 0.187nφ Furnace temperature: 1
500 to 2200°C First, under the above equipment and conditions (here, the hot air temperature is set to 12000°C), the position of the burner 7 in the blow vibe 10 (the distance from the interface 11b between the tuyere 11 and the blow vibe 10 to the burner tip) “
L) was changed in various ways and the combustion rate of the powdered fuel at each position and the state of adhesion and accumulation of ash on the inner wall of the blow vibrator were investigated, and the results shown in Fig. 3 were obtained.

However, the combustion rate is the total thermal burning rate determined from the distribution of CO concentration and velocity distribution during combustion, and the local combustion rate is determined from the ash content balance determined from the dust in the reactor core. In order to calculate the total combustion rate, the CO2 concentration measurement position was set at a point 0.8W1 downstream from the tip surface 11a of the water-cooled tuyere 11. This position corresponds to the raceway depth in an actual blast furnace,
It is necessary to completely burn the powdered fuel before reaching this position. In addition, the amount of ash deposited 5 hours after the start of the experiment [% of the area of ash deposited part in the cross-sectional area of the blow vibe: measured value after taking a photo from the peephole 14]
(See Figure 4)]. As is clear from Figure 3, when liquid fuel (heavy oil) is used, a combustion rate of approximately 92% can be obtained even when the distance L is zero, but when powdered fuel is used at the same distance L, The total combustion rate when used is reduced to about 70%.

In other words, in terms of combustion rate, powder fuel is about 76% of liquid fuel.
(70192 x 100) is being used effectively,
Approximately 114 of the amount of heat remains unburned. However, as the distance L increases, the combustion rate gradually increases, and L
A significant difference clearly appears when the distance is 0.1 m or more, and 0.3
In the range of 0 to 0.35 m, the combustion rate improves by about 20%, making it possible to obtain a combustion rate comparable to that when using liquid fuel. On the other hand, the amount of adhesion and accumulation of ash is hardly observed when L is less than 0.35 m, but increases rapidly when L exceeds 0.35 m.

Along with this, the area through which the hot air passes through the blow vibe 10 decreases, and the combustion rate also tends to decrease. That is, the combustion rate of powdered fuel and the amount of ash deposited are significantly affected by the distance L, and in order to satisfy both at the same time, the distance L must be set between 0.10 and 10.
0.35m. It can be seen that it should preferably be set to 0.20 to 0.35 m1.

Figure 5 shows the results of investigating the relationship between the hot air temperature and the amount of ash deposited when the distance L was set at 0.40 m1 and the hot air temperature was varied from 800 to 1200'C. As is clear from the figure, as long as hot air of 900° C. or lower is used, the problem of ash accumulation hardly occurs. However, when the hot air temperature exceeds 950°C, ash accumulation becomes noticeable. This is thought to be due to the influence of the melting point of the ash contained in the powdered fuel, and is thought to be because at temperatures below 900°C, the ash was hardly melted in the blow vibe and was sent into the furnace. Therefore, in the case of such low-temperature hot air, there is no problem as shown in the present invention, and 9
The present invention is valuable only when hot air of 1050°C or higher is used when the temperature is 50°C or higher. Incidentally, the adhesion and accumulation of ash as described above becomes more pronounced as the inner diameter of the blow vibrator 10 becomes smaller, and when a larger diameter one is used, the amount of adhesion and accumulation itself decreases, and the flow path area is reduced due to ash accumulation. Since the rate of decrease is also small, it is thought that there is relatively little disturbance to the combustion rate.

Therefore, when we investigated the relationship between the internal diameter of the blow vibrator, we found that the problem of ash accumulation becomes noticeable when using a blow vibrator with an internal diameter of 0.18 mφ or less, and there is almost no effect when using a blow vibrator with an internal diameter of 0.18 mφ or less. It was confirmed that the level was negligible. Further, the inner diameter of a blow vibrator used in an actual blast furnace is naturally limited in order to ensure a predetermined amount of hot air and its flow velocity, and the upper limit is generally about 0.18Tr1,φ. Considering these points as well, it can be said that the features of the present invention are effectively exhibited and are sufficient when using a blow vibe with an inner diameter of 0.187TLφ or less. On the other hand, if the inner diameter of the blow vibrator becomes too small, the influence of ash accumulation becomes significant, so it is desirable to use one with a diameter of about 0.13 mφ or more. The present invention is roughly constructed as described above, but the key point is that by properly adjusting the position of the burner for blowing powdered fuel, powdered fuel can be injected without causing any problems due to adhesion or accumulation of ash. This means that the combustion rate can be increased to the level of liquid fuel.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the combustion experiment equipment, Figure 2 is an enlarged view of the main part of the powder fuel injection section in the equipment, and Figure 3 is a graph showing the relationship between the powder fuel injection position, combustion rate, and ash accumulation amount. , Fig. 4 is an explanatory diagram showing the state of ash adhesion to the inner surface of the blow vibrator, Fig. 5
The figure is a graph showing the relationship between hot air temperature and ash pile volume.

Claims (1)

[Claims] 1. A burner for blowing powdered fuel penetrates the wall of a blow pipe for blowing hot air connected to a blast furnace tuyere and enters the blow pipe so that the center of the tip of the burner is near the axis of the pipe. and the powdered fuel blown from the burner,
A method of blowing powdered fuel into a blast furnace through a blast furnace tuyere together with hot air of 1050°C or higher flowing in a blow pipe,
A method for injecting powdered fuel into a blast furnace, characterized in that the tip of the burner is positioned 100 to 350 mm upstream from the boundary between the blast furnace tuyere and the blow pipe.