JPH06102808B2 - Melt reduction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a smelting reduction method for directly producing molten iron from iron ore,
Particularly, it relates to a method for highly efficiently reducing iron ore.

[Prior Art] A typical method of obtaining steel from conventional iron ore is a method combining a blast furnace method and a converter method. This method is a so-called indirect method in which iron ore is reduced by a blast furnace to obtain pig iron, and then this pig iron is decarburized in a converter to obtain steel.

However, this indirect method currently has the following problems.

The coke used in the blast furnace uses strong coking coal, but with the worldwide increase in demand for strong coking coal, there is concern about the availability of strong coking coal and at the same time the price is rising.

A coke oven for coke production is required, and fuel costs are high.

To increase efficiency, expensive sintering equipment is required to sinter the iron ore loaded into the blast furnace.

For this reason, improvements to the indirect method have been proposed, and at the same time, several direct smelting reduction methods that do not use blast furnaces have been developed as alternative steel manufacturing methods to the indirect method.

However, the direct smelting reduction method uses a midrex method (Midrex method) that uses a preliminary reduction furnace to prevent an increase in coal consumption.
Since it is necessary to incorporate a reduced iron manufacturing process such as the above, the equipment cost is high and it has not been put to practical use at this stage.

Further, the direct smelting reduction method of directly reducing iron ore to obtain steel without using a preliminary reduction furnace has the following metallurgical problems.

An iron bath type smelting furnace such as a converter is used to form an iron bath in the furnace, iron ore is added to the iron bath to reduce it, and the gradually increasing iron bath is continuously or intermittently withdrawn to obtain steel. Alternatively, when producing hot metal, a reducing agent is required to reduce iron ore, and when the iron bath is used as the reducing agent, it is a condition that the reduction potential of the iron bath is high.

However, it is common sense that the iron bath to be extracted has a carbon content [C] of less than 1% and has a lower reduction potential than that of a blast furnace with a carbon content [C] of about 4%. The iron ore put in is not immediately reduced even if it dissolves in the iron bath. For this reason, various methods have been tried in which iron ore and coal are charged into an oxygen converter to directly obtain molten steel from the iron ore.

[Problems to be solved by the invention]

The method in which the iron ore and coal are put into an iron bath type smelting furnace to directly obtain molten steel or hot metal from the iron ore is economically far from reduced hot metal in a blast furnace, which is a problem. There is.

In particular, under the condition of almost no secondary combustion, which is equivalent to normal converter operation, the reaction heat of C + 1 / 2O ₂ → CO can be expected to be only about 2200 kcal / Eg · ° C, which exceeds 2000 kcal / T of coal. Further, the CO gas generated by the primary combustion C + O → CO during blowing in the converter reacts with the oxygen jet from the water cooling lance above the surface of the iron bath. In some cases, the heat generated by this secondary combustion is dissipated as a gas, and at the same time, the lance removes a large amount of heat from the cooling water, so that the iron bath is highly adhered. This is because it blocks heat.

Further, conventionally, forced heat generation due to secondary combustion is not considered, and if the secondary combustion ratio expressed by (CO ₂ + H ₂ O) / (CO + CO ₂ + H ₂ + H ₂ O) increases, This is also because the heat deposition efficiency is lowered as shown in FIG. 5 and the secondary combustion heat cannot be effectively utilized. This is because the secondary combustion reaction CO + 1 / 2O ₂ = CO ₂ generates heat more than twice that of the primary combustion of about 5600 kcal / kgfc, and the heat input increases dramatically, while the heat transfer area and heat transfer However, if it is the same as that of the conventional converter, the heat generation efficiency is inevitably lowered, and the gas temperature is generated from the upper part of the furnace without significantly lowering from a very high temperature of 2,000 to several hundred degrees Celsius.

The present invention has been made to solve the above problems, and economically obtain steel directly from iron ore by increasing heat transfer efficiency by increasing the heat transfer area by secondary combustion in a slag bath. The purpose is to propose a smelting reduction method capable of

[Means for solving problems]

In the smelting reduction method according to the present invention, oxygen is blown into the iron bath from a bottom blowhole provided at the bottom of an iron bath type smelting furnace for producing iron ore and coal in an iron bath to produce bath steel or hot metal. Simultaneously with the secondary combustion, oxygen for secondary combustion is blown from an oxygen tuyere provided on the side wall of the furnace above the surface of the iron bath to form a secondary combustion zone above the level of the molten metal in the furnace. The heat transfer efficiency is improved by increasing the heat transfer area by secondary combustion in the slag bath by flying the slag and iron bath generated by the splash gas that is blown from the tuyere for splash generation provided on the side wall of the furnace near the surface. Is the way.

[Action]

In the present invention, instead of the water-cooled lance that blows up acid, oxygen is blown in for primary combustion by means of the bottom blowhole,
Preventing heat removal from the furnace by the water cooling lance and improving the secondary combustion ratio by blowing oxygen for secondary combustion, and at the same time secondary splashing by splashing droplets in the secondary combustion zone. The heat generated thereby is absorbed by the droplets to improve the heat deposition efficiency.

〔Example〕

1 and 2 show an embodiment of the present invention. FIG. 1 is a sectional view and FIG. 2 is a plan view. In the figure, 1 is a converter as an iron bath type smelting furnace. 2 is an iron bath in the converter 1, 3
Is a bottom blowing port provided at the bottom of the converter 1, and 4 is a bath surface 2a of the iron bath 2.
It is an oxygen tuyere provided on the upper side wall of the furnace. Oxygen tuyere 4
Is formed so that the air outlet faces toward the center of the molten metal surface. 5
Is a tuyere for generating splashes provided near the molten metal surface 2. Although it does not substantially participate in the reaction, when blowing oxygen, its tuyere is cooled with water, or by blowing a known protective gas (hydrocarbon gas, inert gas, etc.) around the tuyere, It goes without saying that mouth protection measures will be taken.

Iron ore and coal are continuously charged into the converter 1 configured as described above, high-pressure oxygen is blown into the iron bath 2 from the bottom blowhole 3 of the converter 1, and primary combustion of C + O → CO is performed. To reduce.

This CO gas is generated by the oxygen blown from the bottom blowing port 2nd combustion is also performed, but oxygen is blown from the oxygen tuyere 4 into the secondary combustion zone 6 that is performing this secondary combustion,
The secondary combustion is promoted, the secondary combustion ratio is improved, and the amount of heat generated by the secondary combustion is increased.

On the other hand, a gas for splashing, such as oxygen or argon, is blown from the tuyere 5 for generating splashes, and a part of slag (not shown) on the iron bath 2 and the molten metal surface 2a of the iron bath 2 is made into droplets 7, and this liquid Drop 7 is dropped onto secondary combustion zone 6. Secondary combustion zone 6
The droplets 7 blown up to absorb the heat generated by the secondary combustion, and heat this heat to the iron bath 2.

FIG. 3 shows the result of analyzing the gas discharged from the actual converter 1 and examining the change in heat deposition efficiency with respect to the secondary combustion ratio in this example.

As is clear from FIG. 3, even if the secondary combustion ratio is high, the heat-adsorption efficiency is 75% or more, and the secondary combustion lamp can be efficiently heat-heated on the iron bath 2.

In the above embodiment, the oxygen tuyere 4 and the splash producing tuyere 5 are provided so as to face each other. However, as shown in FIG. 4, the oxygen tuyere 4 and the splash producing tuyere 5 are transferred. Even if the droplets 7 are provided on the same side wall of the furnace 1 and fly to the secondary combustion zone 6, the same operation as in the above embodiment can be performed.

Furthermore, in each of the above-mentioned embodiments, the case where the splashing-forming tuyere 5 is provided below the molten metal surface 2 is shown. However, even if the splashing-generating tuyere 5 is provided above the molten metal surface 2, droplets are generated in the secondary combustion zone. 7
Can be skipped.

〔The invention's effect〕

As described above, the present invention prevents heat removal by the water-cooling lance by using the bottom blowing tuyeres instead of using the water-cooling lance for blowing oxygen for the primary combustion, and prevents the secondary combustion of oxygen for the secondary combustion. The secondary combustion ratio can be improved by blowing into the combustion zone.

Further, by simultaneously flying the slag and the liquid droplets of the iron bath in the secondary combustion zone, the heat generated by the secondary combustion is absorbed by the liquid droplets and heats the iron bath to improve the heat deposition efficiency. You can Therefore, the coal basic unit (kg / ton iron) can be greatly reduced.

In addition, since the heat generated by the secondary combustion is efficiently applied to the iron bath, the temperature of the gas produced by combustion is reduced from 2,000 to several hundred degrees Celsius to around the bath temperature, and the effect of preventing damage to the furnace refractory due to the secondary combustion is also achieved. Have.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view of the above embodiment, FIG. 3 is a characteristic diagram of secondary combustion ratio and heat transfer efficiency according to the above embodiment, and FIG. FIG. 5 is a sectional view showing an embodiment, and FIG. 5 is a characteristic diagram of a conventional secondary combustion ratio and heat-transfer efficiency. 1 ... Converter, 2 ... Iron bath, 3 ... Bottom blowing tuyer, 4 ... Oxygen tuyering, 5
... tuyeres for generating splash, 6 ... secondary combustion zone, 7 ... droplets.

Claims (1)

[Claims] 1. Primary combustion is carried out by blowing oxygen into the iron bath from a bottom blowhole installed in the bottom of an iron bath type smelting furnace for producing iron ore and coal into the iron bath to produce bath steel or bath pig iron. At the same time, oxygen for secondary combustion is blown from an oxygen tuyere provided on the side wall of the furnace above the surface of the molten metal to form a secondary combustion zone above the level of the molten metal inside the furnace, and this secondary combustion zone is provided on the side wall of the furnace near the surface of the molten metal. A smelting reduction method characterized in that the droplets of the slag and iron bath generated by the splash gas blown from the splash-forming tuyere are blown.