JPH04202708A - Method for injecting powdery fuel into blast furnace - Google Patents

Abstract

PURPOSE:To prevent stickness of ash components to a blow pipe and a tuyere by controlling an oxygen content in a carrier gas based on combustibility of powdery fuel and a peripheral temp. at the time of injecting the powdery fuel together with the carrier gas from the tuyere in a blast furnace. CONSTITUTION:The powdery fuel discharged from a powdery fuel supplying equipment 5 in the fixed quantity each, is fed into an injecting nozzle 3 from a supplying pipe 7 together with the carrier gas through a gas feeding pipe 6 and injected into the blast furnace from the tuyere 1 through a blow pipe 2. Then, the oxygen content in the carrier gas is measured with an oxygen concn. metal 9 based on the combustibility of powdery fuel and the peripheral temp., and by adjusting each of valves 10, 11 for adjusting flow rates, inert gas (N2 gas, etc.) is mixed into the carrier gas and controlled so that the oxygen concn. in the carrier gas becomes the prescribed value. By this method, the ash components from the powdery fuel are prevented from being stuck to inner faces of the blow pipe 2 and the tuyere 1, and thereby stable operation of the furnace and reduction of pig iron cost, are obtd.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention controls the oxygen content in the powder fuel carrier gas in a method of injecting powder fuel such as pulverized coal or coke powder from the blast furnace tuyere. The present invention relates to a method for preventing ash derived from powdered fuel from adhering to blow pipes and siding.

(Prior Art) In recent blast furnace operations, a method of injecting powdered fuel such as pulverized coal into the blast furnace has been put into practical use in order to reduce the fuel consumption rate and stabilize the furnace condition.

Figure 6 is a schematic diagram showing an example of a conventional method for blowing granular fuel, and shows a blow pipe (2) connected to the blast furnace siding (1).
A common method is to blow powdered fuel such as pulverized coal into the furnace together with a carrier gas (mainly air) through a fuel injection nozzle (3) that penetrates the wall of the blow pipe and faces into the blow pipe. .

(4) is a heat insulating ring attached to the inner surface of the tuyere to prevent a drop in air temperature.

However, in this method of injecting powder, the ash content derived from the powder fuel (which contains about 5 to 15%) is melted by combustion heat, etc. This molten material adheres and accumulates on the inner peripheral surface of the heat insulating ring, narrowing the air passage and making it difficult to blow hot air and fuel through the siding.

Conventionally, as a countermeasure against this, methods such as changing the blowing position of the powdered fuel blowing nozzle (3) or changing the blowing angle have been used.

A method of injecting powdered fuel by changing the position of the powdered fuel injection nozzle is described in Japanese Patent Application Laid-Open No. 171509/1983, etc., and the method is to change the combustion rate of powdered fuel between the injection nozzle and the tip of the tuyere. This is a method of reducing ash adhesion to the siding by lowering the amount of ash.

(Problems to be Solved by the Invention) However, the conventional means of changing the nozzle blowing position, changing the blowing angle, etc. have the problem of requiring a large amount of man-hours to modify the blow pipe and increasing production costs. In addition, the combustibility of powdered fuel varies greatly depending on its type, so there is a drawback that it is not possible to respond to this.Furthermore, blast furnaces have different operating conditions, equipment near the tuyere, and powdered fuel injection equipment. The drawback is that the effect is not fully demonstrated.

This invention was made in view of the current state of the conventional technology, and it is possible to use powdered fuel derived from powdered fuel without having to change the nozzle blowing position or angle, and without being constrained by blast furnace operating conditions or equipment conditions. The purpose of this paper is to propose a powder fuel injection method that can effectively prevent the adhesion and accumulation of ash.

(Means for Solving the Problem) This invention controls the oxygen content in the carrier gas based on the combustibility of the powder fuel and the ambient temperature when powder fuel is blown into the blast furnace tuyeres together with the carrier gas. The gist of this paper is a method of preventing ash from adhering to blow pipes and siding.

(Function) Air is generally used as a carrier gas for transporting powdered fuel such as pulverized coal. Powdered fuel is fed from a powdered fuel supply device to a blast furnace together with carrier scum through a pneumatic pipe, and is blown into the furnace through a powdered fuel injection nozzle attached to a blowpipe.

Here, as a method for preventing the adhesion of ash derived from powdered fuel to the blowpipe and siding, the reason for using a means of changing the oxygen content in the carrier gas is as follows.

A method of controlling the oxygen content (oxygen concentration) in the carrier gas is, for example, when air is used as the carrier gas, inert gas (N2 gas, etc.) is mixed with this air, and the mixing ratio of air and inert gas is adjusted. It is possible to adopt a method of controlling by changing the

Here, the target oxygen content in the carrier cassette is determined based on the combustibility of the powdered fuel and its surrounding temperature.

That is, the relationship between the ambient temperature (determined by the blowing conditions) and the combustion rate of various powdered fuels A, B, and C is shown in Figure 1, and the relationship between the oxygen content of the powdered fuel and the combustion rate is shown in Figure 2. As shown in Figure 3, which shows the relationship between the combustion rate of powdered fuel and the amount of ash deposited, the combustion rate of various powdered fuels varies depending on the ambient temperature of the powdered fuel and the oxygen content of the powdered fuel, and the ash content depends on the combustion rate. This is because the amount of adhesion is determined.

In other words, the oxygen content in the carrier gas is determined based on the combustibility of the powdered fuel injected into the blast furnace and the blowing conditions, so as to achieve a combustion rate that does not cause ash adhesion to the blow pipe or siding. .

(Example) Fig. 4 is a schematic diagram showing an example of a powder fuel injection device for carrying out the method of the present invention, and Fig. 5 is a schematic diagram showing an enlarged view of the blow pipe and tuyeres in the same device. , (5)
is powder fuel supply equipment, (6) is pneumatic pipe, (7) is carrier gas (air is used here) supply pipe, (8) is inert gas supply pipe for controlling oxygen concentration in carrier gas, (9) is
) indicates an oxygen concentration meter, and <10) and (11) indicate a flow rate adjustment valve, respectively.

That is, a fixed amount of powdered fuel is cut out from the powdered fuel supply equipment (5) and sent along with transportation air to the blowing nozzle (3) via the pneumatic pipe (6), and then sent to the blower through the blowpipe (2). It is blown into the blast furnace through the mouth (1).

The air for transporting powdered fuel is mixed with inert gas at a predetermined ratio so as to have a target oxygen content that does not cause ash adhesion upstream of the powdered fuel injection equipment, and is supplied to the pneumatic pipe (6). . The oxygen content in the transportation air can be adjusted using the oxygen concentration meter (9) using the transportation air flow rate adjustment valve (1).
0) and the inert gas flow rate adjustment valve (11).

The powdered fuel that is injected together with the air for transporting powdered fuel in this way is derived from powdered fuel as a result of proper combustion between the tip of the blowing nozzle and the tip of the blade in the blow pipe (2). Ash content is inside the blowpipe (2) and the tuyere (
1) It does not adhere to the inner surface, and even if it does, the effect on hot air and fuel injection into the blast furnace is considered to be almost negligible.

Next, the results obtained when the method of this invention is applied to an actual blast furnace will be explained.

Example 1 The method shown in Fig. 1 was applied to a blast furnace with an internal volume of 2700 m3, air was used as the carrier gas, N2 was used as the residue for adjusting the oxygen content in the air, and pulverized coal ( Ash content 1
0.3%) was injected. Table 1 shows the blast furnace operating conditions at that time.

In this example, as a result of blowing pulverized coal with an oxygen content of 15% in the carrier gas, almost no ash was observed inside the blow pipe and the tuyere. On the other hand, when the oxygen content was set to 9%, ash adhesion and growth occurred.

Example 2 The blast furnace operating conditions were changed as shown in Table 2 (blow temperature was increased to 1
As a result of injecting pulverized coal in the same manner as in Example 1, no ash adhesion to the blow pipe or siding was observed even in this example when the oxygen content in the carrier gas was 10%. Ta. On the other hand, when the oxygen content was reduced to 4%, ash adhesion and growth occurred.

Example 3 Under the blast furnace operating conditions shown in Table 1, pulverized coal (ash content 11.5%) was injected in the same manner as in Example 1. As a result, the blowpipe and Although no ash was observed on the siding, the oxygen content was reduced to 1
When the content was set at 3%, ash adhesion and growth occurred.

Table 1 Table 2 (Effects of the Invention) As explained above, this invention improves the air flow from the tip of the injection nozzle to the tip of the tuyere by adjusting the oxygen content in the carrier gas of the powdered fuel injected into the blast furnace. Control the combustion situation,
Since this method prevents ash derived from powdered fuel from adhering to the blow pipe and siding, it can easily accommodate changes in the type of powdered fuel and ventilation conditions without being restricted by blast furnace equipment conditions. This has a great effect on stable operation of blast furnaces and reduction of pig iron costs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between ambient temperature and combustion rate of various powdered fuels in this invention, Figure 2 is a diagram showing the relationship between oxygen content and combustion rate of various powdered fuels, and Figure 3 is the same. A diagram showing the relationship between the combustion rate of various powdered fuels and the amount of ash deposited. Fig. 4 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention. Fig. 5 shows the blow pipe and lining of the same apparatus. FIG. 6 is an enlarged schematic sectional view showing an example of a conventional powder fuel injection method. DESCRIPTION OF SYMBOLS 1... Tuyere, 2... Blow pipe, 3... Fuel injection nozzle, 5... Powdered fuel supply equipment, 6... Pneumatic pipe, 7... Carrier gas supply pipe, 8 ... Inert gas supply pipe, 9 ... Oxygen concentration meter, 10.11 ... Flow rate adjustment valve. Patent applicant Sumitomo Metal Industries Co., Ltd. Agent 1) Yoshihisa! 1 Figure 1 Ambient temperature of powdered fuel (°C) Figure 2 Oxygen content of powdered fuel (%) Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A method of injecting powdered fuel together with a carrier gas from a blast furnace tuyere, characterized in that the oxygen content in the powdered fuel carrier gas is controlled based on the combustibility of the powdered fuel and the ambient temperature. How to inject body fuel.