JPH0959705A - Blast furnace operation method - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a method for improving the combustibility of pulverized coal by a simple means without changing the blowing condition. [Composition] A lance for blowing pulverized coal is inserted into a blast furnace tuyere or a blow pipe connected to the blast tuyere, and the pulverized coal discharged from the lance is blown into the blast furnace by a hot air flow from the blow pipe. 2 lances to fit
As a heavy pipe structure, pulverized coal is blown from the inner pipe and gas is blown from the outer pipe to provide a relative position difference between the inner pipe and the outer pipe, and the mass flow rate of gas blown from the outer pipe is increased to burn the pulverized coal burned. Control sex.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a blast furnace for producing pig iron, and more specifically, in a pulverized coal blowing operation from a tuyere, the dispersibility of the pulverized coal injected can be simplified. The present invention relates to a method for improving the combustibility of pulverized coal by controlling it by means so as to stably operate the blast furnace.

[0002]

2. Description of the Related Art Conventionally, as a mode of operation of a blast furnace, a large amount of liquid fuel such as heavy oil or tar is blown into a blower tuyere (hereinafter, also simply referred to as tuyere) to reduce the coke ratio and the tap ratio. The operation to raise has been performed. However, as a result of the drastic change in the energy price system due to the soaring crude oil price in the 1970s, all coke operation became the mainstream of blast furnace operation.

With all-coke operation, fuel costs are lower than with liquid fuel injection. However, since the theoretical combustion temperature before the tuyere becomes high and the amount of hydrogen input to the blast furnace decreases, the unloading becomes unstable, slips frequently occur, and the blast pressure rises or fluctuates, causing instability. I was forced to run. Until now, such problems have been dealt with by adjusting the humidity from the tuyere, but the operation of increasing the humidity leads to an increase in the coke ratio, and also increases the basic unit of blown air, which causes the limit of blow-through. There was a limit that the maximum tap ratio was limited.

On the other hand, in a situation where the production capacity of a coke oven becomes insufficient, an increasing number of blast furnaces employ pulverized coal as an inexpensive tuyere blowing fuel in order to solve the above problems. If such a pulverized coal blowing operation is performed, both a decrease in coke ratio and an increase in maximum tap ratio can be realized.
Problems related to moisture adjustment from the tuyere are solved.

[0005] Against this background, a larger amount of pulverized coal is now in operation, and some blast furnaces can also inject 200 kg of pulverized coal per ton of pig iron (hereinafter referred to as 200 kg / pt). It has become. Problems such as a large amount of pulverized coal blowing operation and combustion of pulverized coal in the raceway part have been highlighted in order to further increase the amount of pulverized coal blowing.

Generally, for blowing pulverized coal, a pulverizing coal blowing lance is inserted into the blast tuyere of a blast furnace or a blow pipe connected to the blowing tuyere, and the pulverized coal discharged from the lance is heated with hot air from the blow pipe. It is carried out by carrying it to the raceway space at the tip of the tuyere. Only the pulverized coal burns at the tuyere and blow pipe, and the simultaneous combustion reaction of pulverized coal and coke proceeds in the raceway space.

In the operation of blowing a large amount of pulverized coal, the ratio of pulverized coal to oxygen becomes large, stoichiometrically, pulverized coal does not burn (gasify), and oxygen is consumed by coke in the raceway. Therefore, it is inevitable that pulverized coal, which is not burnt on the raceway, so-called unburned char is generated. The unburned char rises in the furnace along with the gas flow from the raceway, and traps in the cohesive zone and drops FeO.
Reaction between (FeO + C = Fe + CO ), solution loss reaction with _{CO 2 (CO 2 + C =} 2CO) is considered to be consumed due to, some of furnace core portion, cohesive zone root, the shaft portion It is considered that the gas stays in the furnace and deteriorates air permeability, and is discharged as furnace top dust together with waste gas from the furnace top.

When unburned char is stayed in the furnace or discharged from the furnace in this way, the pulverized coal blown in is not effectively used as a fuel, so that the function of replacing a part of the coke cannot be achieved. The effect of blowing pulverized coal will be diminished. Therefore, it is necessary to take measures to increase the combustion efficiency of the blown pulverized coal.

In general, in order to increase the combustion efficiency of pulverized coal, firstly, it is effective to change the blast conditions, specifically, to raise the blast temperature and enrich oxygen. Costs rise. The second method is to increase the dispersibility of pulverized coal and accelerate the reaction with oxygen by changing the mounting position of the lance or the shape of the lance under a given blowing condition. The increase causes abrasion of tuyere and melting and adhesion of ash in pulverized coal to the tuyere.

An optimum blowing method is being sought in such a complicated constraint condition.
Japanese Patent No. 213406 discloses a method of controlling the combustion amount by forming a pulverized coal blowing lance into a concentric double tube and adjusting the oxygen concentration of combustion air supplied from an outer tube. This alleviates the first problem by the second method.

Further, in Japanese Patent Laid-Open No. 6-330113, a plurality of lances are inserted into a blow pipe so that the center axis of the lance does not intersect with the center axis of the blow pipe. Although a method of increasing the diffusion efficiency of is disclosed, this belongs to the second method.

[0012]

Among the methods for improving the burning rate of pulverized coal as described above, the method disclosed in Japanese Patent Laid-Open No. 213406/1990 leads to efficient oxygen enrichment. However, even if the amount of pulverized coal blown is 100 kg / pt or less, the amount of oxygen from the outer tube is 2 to the carrier gas amount of pulverized coal.
When the pulverized coal is blown in a large amount and the oxygen enrichment amount becomes large, there is a limit to the blowing amount from the outer circumference of the blowing lance due to an increase in pressure loss.

Further, in the method disclosed in Japanese Patent Laid-Open No. 6-330113, since a plurality of lances are inserted into one tuyere, the blowing system is complicated, and the blow pipe and the tuyere are not provided. The likelihood of ash deposits increases.

The present invention has been made in view of these problems, and an object thereof is to provide a method for improving the combustibility of pulverized coal by a simple means without changing the blowing conditions. To do.

[0015]

The inventors of the present invention have used a lance of a concentric double pipe to blow pulverized coal from an inner pipe and blow gas (eg, air) from an outer pipe into a tip structure of the lance. By changing the relative position of the tip of the inner tube and the tip of the outer tube, and by changing the amount and flow rate of the gas blown from the outer tube, the dispersibility of the pulverized coal blown from the inner tube is changed. We obtained the knowledge that the That is, by using a cold experimental apparatus simulating a tuyere / blow pipe section equipped with a concentric double tube lance, the above-mentioned factors, that is, the tip structure of the lance, the amount and the flow rate of the gas blown from the outer tube, are pulverized coal. By investigating the effect on the dispersion of
The above solution was found.

Therefore, the means for solving the above problems according to the present invention is to insert a pulverized coal blowing lance into the blast tuyere of the blast furnace or a blow pipe connected to the blast tuyere, and to discharge the pulverized coal from this lance. Is blown into the blast furnace by the hot air flow in the blow pipe, the lance has a double pipe structure, and pulverized coal is blown from the inner pipe and gas is blown from the outer pipe, and the relative position of the inner pipe and the outer pipe, and / or By controlling the mass flow rate of gas blown from the outer pipe and / or the gap distance between the outer pipe and the inner pipe, the dispersibility of the blown pulverized coal, that is, the combustibility is controlled.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the effect of the relative position difference between the tip of an inner tube and the tip of an outer tube on the dispersibility of pulverized coal. Here, the relative position difference (l) is indicated by a plus (+) when the outer pipe is protruding from the inner pipe and a minus (-) when the inner pipe is protruding. Also,
The pulverized coal dispersion rate is expressed as the abundance of pulverized coal in the blow pipe cross section. In addition, "h" in FIG. 1 is a gap distance between the inner and outer tubes.

As is clear from this result, when the double tube lance is used, the dispersibility of pulverized coal is improved as compared with the single tube lance, and the degree of improvement is different depending on the relative position difference (l). In the case of using the double pipe lance, the dispersibility is not good when the relative position difference between the inner pipe tip and the outer pipe tip is negative, but the dispersibility is improved when it is positive. But,
It has been found that when the positive value of the relative position difference exceeds the outer diameter of the inner pipe and becomes 1> 18 mm, the effect of improving the dispersibility is saturated and, at the same time, the pulverized coal becomes clogged, which is not preferable. Therefore, the relative position difference (l) is 1 = 0 to the inner pipe outer diameter (m
m) is preferable.

FIG. 2 shows the mass flow rate of the gas blown from the outer tube.
The influence of (W) on the dispersibility was investigated by using the gap distance (h) between the outer pipe and the inner pipe, that is, the half of the difference between the outer pipe inner diameter and the inner pipe outer diameter as a parameter. From the figure, it is clear that the higher the mass flow rate of gas and the smaller the gap distance between the outer tube and the inner tube, the better the dispersibility, but W / h, that is, the gas flux is 2.0 × 10 ⁵ kg. The effect saturates when the value exceeds / m ² · H. Further, since the operation of improving the dispersibility involves an increase in the amount of blown gas and the pressure loss of the blown gas, it is desirable to select the amount of operation required to obtain the required dispersibility.

[0020]

EXAMPLE In this example, the case where the present invention is applied to an actual blast furnace (internal volume 2700 m ³ ) will be described. The blowing conditions at this time are as shown in Table 1. The adjustment of the temperature before the tuyere was performed by enriching oxygen. Table 2 shows the results of the operating conditions and the pulverized coal combustion rate.

[0021]

[Table 1]

Under these conditions, the effect of the present invention was confirmed by changing the specifications of the pulverized coal blowing lance as shown in Table 2. The effect was confirmed by evaluating the burning rate of pulverized coal. For the burning rate of pulverized coal, insert a sonde that can sample the inside of the raceway at a predetermined position, and use the collected unburned pulverized coal for analysis to determine the carbon / ash content of the sample before and after the reaction.
It was calculated from the change in the Al ₂ O ₃ ratio. Needless to say, the method for calculating the combustion rate of pulverized coal is not limited to this method (chemical analysis method using Al ₂ O _{3 in} ash as a tracer), and other components may be used as tracers and the collected material may be used as an image. It is also possible to select a method such as calculating the combustion rate by processing.

The conventional example is an example in which a normal single tube lance is used without using a double tube for the pulverized coal blowing lance. The burning rate in this case is about 30% at the tuyere tip + 250 mm
At the back of the raceway (tuyere tip + 750 mm), it is almost 60%
Met.

On the other hand, in case 1 adopted in the method of the present invention, the pulverized coal blowing lance is a double pipe and the relative position difference between the outer pipe and the inner pipe is +15 mm. The sign (+-) of the relative position difference is the same as the sign in the cold experimental device in the previous section. In this case, since the dispersibility of the pulverized coal near the lance discharge portion was improved, the burning rate was +25
About 35% at 0 mm, inside the raceway (tuyere tip + 750 mm)
Has risen to almost 65%.

In case 2, the flow rate of gas from the outer tube is 1.5 times that in case 1, and the difference in inner diameter between the outer tube and the inner tube is reduced by 1 mm from case 1. In this case, the dispersibility of the pulverized coal near the lance discharge part was further improved, and the combustion rate was about 40% at the tuyere tip + 250 mm.
At the back of the raceway (tuyere tip + 750 mm), almost 70%
Rose.

Further, the present inventors have confirmed that the present invention is also effective when oxygen-enriched air is sent from the outer tube as seen in the prior art. In the comparative example, Table 1
The amount of oxygen that meets the blast conditions of was not enriched in the blast, but was supplied as oxygen from the outer tube. In that case, the burning rate is about 33% at the tuyere tip + 250 mm, which is far behind the raceway.
It was almost 63% at (tuyere tip + 750 mm), confirming the improvement effect compared to the conventional example.

In case 3, the lance condition of case 2 was applied to the blowing condition of the comparative example. As a result, the burning rate of pulverized coal increased to about 45% at the tuyere tip +250 mm and to almost 80% at the back of the raceway (tuyere tip +750 mm).

[0028]

[Table 2]

[0029]

As described above, according to the method of the present invention, it is possible to improve the burning rate of pulverized coal with a simple device during the operation of blowing pulverized coal from the tuyere of the blast furnace. It is possible to avoid the deterioration of the air permeability due to the retention in the furnace and the decrease of the replacement rate with the coke due to the discharge to the outside of the furnace, to realize the stable operation of the blast furnace and to reduce the cost.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the relative positional difference between an outer pipe and an inner pipe when using a double pipe lance on the dispersibility of pulverized coal.

FIG. 2 is a graph showing the influence of the mass flow rate of gas blown from the outer tube and the gap distance between the outer tube and the inner tube on the dispersibility of pulverized coal when the double tube lance is used.

Claims (2)

[Claims] 1. A pulverized coal blowing lance is inserted into a blast furnace tuyere of a blast furnace or a blow pipe connected to the blast tuyere, and the pulverized coal discharged from the lance is introduced into the blast furnace by a hot air flow from the blow pipe. The lance has a double tube structure, the pulverized coal is blown from the inner tube, and the gas is blown from the outer tube to provide a relative position difference between the inner tube and the outer tube and adjust the relative position difference. A method for operating a blast furnace, which comprises controlling the combustibility of pulverized coal blown. 2. The blast furnace operating method according to claim 1, further comprising adjusting a mass flow rate of gas blown from the outer tube and / or a gap distance between the outer tube and the inner tube.