JP2868921B2 - Operation method of smelting reduction furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing pig iron by mixing a pre-reduced fine ore with a carbonaceous material, introducing oxygen, and reducing it by melting.

[0002]

2. Description of the Related Art In such a smelting reduction method, in order to promote the reaction, O ₂ , CO ₂ , and N ₂ gas are blown under a bottom as described in, for example, JP-A-62-224617. It is known to

[0003]

However, in the case of bath stirring by bottom-blowing, when an oxidizing gas such as O ₂ or CO ₂ is used as a stirring gas, solid carbon in the bath is oxidized. When the unit consumption of coal increases, and when an inert gas such as N ₂ gas is introduced, it is necessary to introduce it from outside the process system, and moreover, it increases the sensible heat to compensate for the temperature decrease due to the introduction. Energy is required, which is not preferable in terms of heat economy.

[0004] The problem to be solved in the present invention is to find a means for eliminating disadvantages such as consumption of carbonaceous material and energy loss when blowing a stirring gas in the smelting reduction of preliminarily reduced fine ore. .

[0005]

SUMMARY OF THE INVENTION According to the present invention, a part of an exhaust gas in a smelting reduction furnace is separated and recovered, and pulverized coal is blown into the exhaust gas to transform the exhaust gas. It is characterized in that it is blown into the bath as a working gas.

[0006]

In the smelting reduction furnace, blowing acid is supplied to supply heat required for the reduction and melting of the ore, and CO, which is generated by the reduction of the ore and a part of the gas generated by the decomposition of the coal, is burnt with CO, High-temperature exhaust gas containing CO ₂ , H ₂ , and H ₂ O as main components and having a temperature of about 1700 to 2000 ° C. is generated. By blowing pulverized coal into the separated and recovered high-temperature exhaust gas, the pulverized coal is thermally decomposed and the formula (1),
An endothermic gas reforming reaction as shown in (2) occurs, and the exhaust gas is transformed into a gas having lower temperatures of CO and H ₂ as main components.

C _m H _n + mCO ₂ → ₂ mCO + (n / 2) H ₂ (1) C _m H _n + mH ₂ O → mCO + (m + n / 2) H ₂ (2) The transformed gas still has a temperature of 1000 ° C. or more. Since the temperature is high, it is passed through a heat exchanger to effectively use sensible heat, and after the temperature is further lowered, the flow rate is adjusted and used as a gas source for stirring. The gas thus reformed contains CO and H ₂ as main components which do not decarbonize the carbon in the hot metal even when blown into the hot metal, and a small amount of an oxidizing gas such as CO ₂ and H ₂ O. Although there is a possibility of remaining carbon, pulverized coal is injected in an amount sufficient to modify them, so that carbon in the hot metal is hardly decarburized. Moreover, since the pulverized coal used in the system as the gas in the system is used as the reforming material as the gas for stirring as described above, no special equipment for gas procurement and conversion is required.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to a top-blowing converter type smelting reduction furnace will be described.

FIG. 1 shows an outline of the equipment.

In FIG. 1, reference numeral 1 denotes an iron bath furnace, from which a prereduced ore and coal are charged into the iron bath furnace 1 through a raw material charging port 3 attached to an exhaust gas duct 2 above the iron bath furnace. Oxygen is blown from the lance 4 to form a metal bath and a slag bath at the bottom. A branch pipe 5 is formed in the exhaust gas duct 2, and an inlet 6 for charging pulverized coal is opened at an inlet of the branch pipe 5. The introduced pulverized coal reacts with O ₂ and CO _{2 in} the exhaust gas at 1800 ° C. to be transformed, and when the temperature has dropped to 1100 ° C., the temperature is lowered to 900 ° C. through the heat exchanger 7 and the iron bath furnace 1 Is blown into the bath from a blowing port 8 provided at the bottom of the bath. Reference numeral 9 denotes a bypass passage for coping with a change in capacity due to the conversion of exhaust gas.

In the above apparatus, a measuring device 10 for measuring the flow rate of the exhaust gas and the degree of oxidation (secondary combustion rate) is provided at the entrance of the exhaust gas duct of the iron bath furnace 1.

At the inlet of the branch pipe 5, a part of the exhaust gas is introduced, and a required amount of pulverized coal is introduced based on the oxidation degree and the flow rate measured by the measuring device 10, and CO ₂ and H ₂ in the exhaust gas are introduced.
Converts ₂ O into CO and H ₂ gas. The amount of the transformed gas is adjusted at the branch point of the branch pipe 5 with the bypass 9 so that the iron bath furnace 1
Is blown from the blow-in port 8 as a bath stirring gas.
Charged pulverized coal is not involved in all the shift reaction, believed gas blown as a bath agitation gas from the blowing inlet 8 is in a state CO ₂ and H ₂ O, it where the pulverized coal mixed, CO ₂ And the presence of H ₂ O, the input pulverized coal is activated even though it is slightly oxidizing, and has a recharging ability.

[0013]

According to the present invention, the following effects can be obtained.

(1) It is possible to suppress the decarburization of carbon in the iron bath in the smelting reduction furnace to a low level, and to perform an operation with a high secondary combustion rate, thereby improving the operation capacity of the furnace.

(2) Since the consumption of fixed carbon can be reduced, the unit consumption of coal can be reduced.

(3) Since the gas in the system can be used as the stirring gas, no equipment for introducing the gas is required.

(4) The energy required for increasing the sensible heat of the stirring gas can be reduced.

(5) By using the reforming of the exhaust gas in combination, the quality of the exhaust gas can be improved as compared with the case where an inert gas such as N ₂ is contained.

[Brief description of the drawings]

FIG. 1 shows an outline of a smelting reduction furnace used for carrying out the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron bath furnace 2 Exhaust gas duct 3 Raw material input port 4 Oxygen injection lance 5 Branch pipe 6 Pulverized coal input port 7 Heat exchanger 8 Stirring gas injection port 9 Bypass passage 10 Exhaust gas measuring device

Claims (1)

(57) [Claims] 1. A method of separating and recovering a part of an exhaust gas in a smelting reduction furnace, injecting pulverized coal into the exhaust gas to transform the exhaust gas, and blowing the gas into a bath as a stirring gas for the smelting reduction furnace. Operating method of reduction furnace.