JP2869986B2 - Smelting reduction method of iron ore - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for smelting and reducing iron ore using an iron-bath smelting reduction furnace.

[Prior Art] An iron-bath smelting reduction furnace in which iron ore and carbon material are supplied into a converter type smelting reduction furnace in which an iron bath is accommodated, and oxygen is blown through a lance to reduce the iron ore by smelting. There is known a method for smelting reduction of iron ore by using a method.

FIG. 3 is a schematic vertical sectional view of an iron-bath smelting reduction furnace.
As shown in FIG. 3, the smelting reduction furnace is a converter type furnace body 1.
A lance 2 vertically inserted into the furnace through the opening 1a of the furnace body 1, a stirring gas inlet 3 provided on the bottom wall and / or side wall of the furnace body 1, and a hood 4 covering the furnace port 1a. And a chute 6 for supplying a carbonaceous material such as coal and the like.

A predetermined amount of molten iron is accommodated in the furnace, iron ore is supplied through the chute 5, and carbonaceous materials such as coal and flux are supplied through the chute 6 into the furnace. Oxygen gas is blown from a furnace port 1a through a lance 2 vertically inserted into the furnace body 1 onto a slag 8 in the furnace, and nitrogen gas or the like is introduced into an iron bath 7 in the furnace through a gas inlet 3 for stirring. Of stirring gas.

As a result, the carbon in the molten iron and the carbon in the supplied carbonaceous material react with the oxygen gas blown through the lance 2 as shown in the following formula (1) to generate CO gas.

The CO gas generated as described above reacts with the oxygen gas blown through the lance 2 as shown in the following equation (2) to produce CO ₂
It becomes gas, and at this time, heat having a high calorific value is generated.

The heat of this CO ₂ gas is transferred to the iron bath 7 via the slag 8. Therefore, the iron ore in the iron bath 7 is melted and reduced by the carbon in the carbonaceous material to hot metal. In FIG. 3, reference numeral 9 denotes a duct for discharging exhaust gas whose one end is connected to the hood 4.

During the refining by smelting reduction as described above, there is a problem that sloping occurs in which molten iron or slag is jetted. When the slopping occurs, the spilled molten iron or slag adheres to and blocks the furnace port 1a, making it impossible to operate, impairing productivity and lowering the iron yield. Therefore, it is extremely important to prevent the occurrence of slopping during refining by the smelting reduction method.

[Problem to be Solved by the Invention] The cause of the occurrence of slopping is considered as follows. That is, if the amount of carbon present in the bath is small due to the carbon material supplied into the furnace, the reduction of iron ore is delayed and the
As a result of the increase in the amount of FeO, the slag is likely to form and slopping occurs.

Therefore, if the carbon material is supplied so that an appropriate amount of carbon always exists in the bath, it is possible to prevent the occurrence of slopping.

Therefore, conventionally, a carbon material has been supplied into the furnace in the following manner so that an appropriate amount of carbon is present in the bath. That is, the exhaust gas discharged from the furnace through the duct 9, ie, CO 2
The amount of gaseous carbon in gas and CO ₂
Is measured by an exhaust gas analyzer 10 provided in the middle of the measurement.
The total amount of the gaseous carbon amount in the obtained exhaust gas, the carbon amount dissolved and consumed in the molten iron, and the powdery carbon amount mixed as dust in the exhaust gas discharged through the duct 9; The amount of carbon remaining in the bath is calculated from the amount of carbon material supplied into the furnace. The carbonaceous material is supplied into the furnace such that the amount of residual carbon in the bath thus obtained has an appropriate value that does not cause slopping.

However, in the above-mentioned conventional method, the amount of powdered carbon mixed and discharged as dust in the exhaust gas is:
You have to rely on empirical estimates. Therefore, the accuracy of the residual carbon amount in iron calculated as described above is low.

As a result, an appropriate amount of carbon cannot be left in the bath, and if the amount of remaining carbon is small, slopping occurs. On the other hand, if an excessive amount of carbon material is charged, a reaction of CO ₂ + C → 2CO occurs due to volatile carbon from the coal, and the OD ratio (the degree of oxidation of generated gas in the reduction furnace) decreases. As a result, the unit temperature of carbonaceous material per ton of pig iron increases due to a decrease in the temperature of the molten iron.

Therefore, an object of the present invention is to supply an appropriate amount of carbon material into a furnace so that the amount of residual carbon in a bath becomes an appropriate value, thereby preventing the occurrence of slopping and a decrease in OD ratio. It is an object of the present invention to provide a method for smelting and reducing iron ore using a bath-type smelting reduction furnace.

[Means for Solving the Problems] The present invention relates to a method for supplying iron ore and carbonaceous material into an iron-bath smelting reduction furnace and smelting and reducing the iron ore by oxygen blown into the furnace. Dust in the exhaust gas is collected by a dry dust collector provided in the middle of a duct that discharges the exhaust gas from, the collected dust is classified, and mixed into the exhaust gas by the weight of the obtained coarse-grain dust. The amount of powdered carbon that is present is detected, and the amount of gaseous carbon contained in the exhaust gas is measured by an exhaust gas analyzer provided in the middle of the duct. The amount of powdered and gaseous carbon present in the exhaust gas discharged from within, and
From the total amount of carbon dissolved in the bath in the furnace and the amount of carbon material supplied into the furnace, the amount of residual carbon in the bath is calculated, and the remaining carbon amount does not cause slopping. It is characterized in that the supply amount of the carbon material is controlled so as to have an appropriate value, and the fine dust obtained by the classification is reused as an iron source.

Next, the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing one embodiment of the method of the present invention. As shown in FIG. 1, the smelting reduction furnace is a converter type furnace body 1, a lance 2 inserted vertically into the furnace through an opening 1a of the furnace body 1, a bottom wall of the furnace body 1 and / or Conventionally, a gas inlet 3 for stirring provided on the side wall, a chute 5 for charging iron ore and a chute 6 for charging carbonaceous material such as coal provided on a hood 4 covering the furnace port 1a are different from those in the related art. The same is true.

In the middle of a flue gas discharge duct 9 whose one end is connected to the hood 4, a dry dust collector 11 for collecting dust in flue gas and a flue gas analyzer 10 for measuring the amount of carbon in the flue gas. Are provided.

The dry dust collector 11 is connected to a sieving machine 12 for classifying the collected dust, and the sieving machine 12 is provided with a container 13 for accommodating the classified coarse particles and the fine particles. A container 14 for housing is connected. A load cell 15 is attached to each of the containers 13 and 14, and the weight of each of the containers 13 and 14 can be measured by the load cell 15.

In the present invention, dust in the exhaust gas discharged from the furnace is collected by a dry dust collector 11 provided in the middle of the duct 9. The collected dust is classified by the sieving machine 12 into, for example, coarse particles having a particle size of 0.5 mm or more and fine particles having a particle size of less than 0.5 mm.

The components in the dust differ significantly depending on the particle size. That is, as is apparent from the graph of FIG. 2, for example, coarse dust having a particle size of 0.5 mm or more is almost composed of carbon. On the other hand, for example, fine dust having a particle size of less than 0.5 mm has a high iron content and a low carbon content.

Therefore, the container 13 containing the coarse dust is loaded into the load cell 15
By weighing and measuring the weight of coarse dust,
The amount of powdered carbon (dC
₁ / dt) can be detected.

Further, the amount of gaseous carbon (dC ₂ / dt) per unit time contained in the exhaust gas is measured by an exhaust gas analyzer 10 provided in the middle of the duct 9.

Since the amount of carbon material supplied into the furnace per unit time (dC ₃ / dt) dissolved in the iron bath can be obtained by calculation, as described above, the amount of carbon material discharged from the furnace per unit time Of powdered carbon in exhaust gas (dC ₁ / dt), amount of gaseous carbon in exhaust gas per unit time (dC ₂ / dt), and amount of carbon consumption per unit time (dC ₃ / dt) Total amount (dC
_i / dt) and the amount of carbon in the carbonaceous material supplied into the furnace per fixed time period, the amount of carbonaceous material that does not cause slopping can be calculated by the following equation (1).

On the other hand, since the fine dust in the container 14 classified by the sieving machine 12 has a large amount of iron as described above, the fine dust can be charged into the reduction furnace as an iron source and reused.

Example Next, an example of the present invention will be described.

Using an iron-bath smelting reduction furnace (5 Ton), smelting reduction was carried out by the method shown in FIG. 1 under the following conditions. That is, 5 to 6 tons of molten iron are accommodated in a furnace, and nitrogen gas is supplied at 300 N from a stirring gas injection port 3 provided on the bottom and side walls of the furnace body 1.
m ³ / Hr · blowing an amount of _this, the oxygen gas from the lance 2 200
Blowing was performed at an amount of 0 Nm ³ / Hr. Then, iron ore was supplied from the chute 5 at a rate of 60 kg / min, and coal (carbon content: 73%) was supplied from the chute 6 as described below.

That is, the amount of residual carbon in the bath was set to 200 kg at which slopping did not occur. Then, according to the method of the present invention, dC ₁ / dt, dC ₂
Calculate the total amount dCi / dt of / dt and dC ₃ / dt and shoot 6
Supplied coal at a rate of 40-50 kg / min.

Table 1 shows the amount of change in the residual carbon amount and the number of times of occurrence of slopping with respect to the set value (200 kg) obtained as a result, and dCi / dt as an empirical estimate using the conventional method, ie, dC ₁ / dt.
Is calculated, and the fluctuation of the residual carbon amount with respect to the set value and the number of times of occurrence of slopping when coal is supplied are shown.

As is apparent from Table 1, in the case of the method of the present invention,
The amount of change in the residual carbon amount with respect to the set value was small, and no slopping occurred. On the other hand, in the case of the conventional method, the amount of variation of the residual carbon amount with respect to the set value was large, and the slopping occurred 1.5 times per charge.

In the case of the reduction furnace having the above-mentioned capacity, the amount of residual carbon in which slopping does not occur is 100 kg or more.

[Effects of the Invention] As described above, according to the method of the present invention, iron ore and carbonaceous material are supplied into an iron-bath smelting reduction furnace, and are blown through a lance vertically inserted into the furnace from above. When smelting and reducing iron ore with oxygen, it can operate smoothly without slopping, improving iron yield and preventing a decrease in OD ratio, and effectively reducing carbon unit consumption. And other industrially useful effects.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of the method of the present invention, FIG. 2 is a graph showing the relationship between the particle size of dust and components, and FIG.
The figure is a schematic vertical sectional view of an iron bath smelting reduction furnace. In the drawings, 1 ... furnace body, 2 ... lance, 3 ... gas inlet for stirring,
4 ... hood, 5,6 ... shoot, 7 ... molten iron, 8 ...
Slag, 9 duct, 10 exhaust gas analyzer, 11 dry dust collector, 12 sieving machine, 13, 14 container, 15 load cell.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Muroya 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Kenji Takahashi 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Inside Steel Tube Co., Ltd. (72) Inventor, Atsushi Kitagawa 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Tube Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C21B 11/00

Claims (2)

(57) [Claims] 1. A method for supplying iron ore and carbonaceous material into an iron-bath smelting reduction furnace and smelting and reducing the iron ore by oxygen blown into the furnace. Dust in the exhaust gas is collected by a dry dust collector provided on the way, the collected dust is classified, and the amount of powdered carbon mixed into the exhaust gas is detected by the weight of the obtained coarse dust. Further, the amount of gaseous carbon contained in the exhaust gas was measured by an exhaust gas analyzer provided in the middle of the duct, and in the exhaust gas discharged from the furnace obtained in this manner, From the total amount of powdered and gaseous carbon present and the amount of carbon dissolved in the iron bath in the furnace, and the amount of carbon material supplied into the furnace, the amount of carbon remaining in the bath Is calculated so that the residual carbon amount is constant. , And controlling the supply amount of the carbonaceous material, smelting reduction method of iron ore. 2. A method for supplying iron ore and carbonaceous material into an iron-bath smelting reduction furnace and smelting and reducing the iron ore with oxygen blown into the furnace. Dust in the exhaust gas is collected by a dry dust collector provided on the way, the collected dust is classified, and the amount of powdered carbon mixed into the exhaust gas is detected by the weight of the obtained coarse dust. Further, the amount of gaseous carbon contained in the exhaust gas was measured by an exhaust gas analyzer provided in the middle of the duct, and the obtained exhaust gas discharged from the furnace was measured. From the total amount of powdered and gaseous carbon present, and the amount of carbon dissolved in the iron bath in the furnace, and the amount of carbon material supplied into the furnace, the amount of carbon remaining in the bath Is calculated so that the residual carbon amount is constant. To control the supply amount of the carbonaceous material and fine dust obtained by the classification is characterized by reused as an iron source, smelting reduction method of iron ore.