JPH07126724A - Production of sponge iron - Google Patents

Abstract

PURPOSE:To provide a method for producing sponge iron in which the heating time required for reducing is short and the heating energy is less, thus, the production cost is inexpensive. CONSTITUTION:In the method for producing sponge iron by packing powdery iron oxide 2 and a powdery reducing agent 3 into a vessel 1 made of refractories and subjecting only the vessel 1 to indirect heating from the outside to reduce and sinter iron oxide, the powdery iron oxide 2 and powdery reducing agent 3 are previously mixed and are thereafter packed into the vessel 1 made of refractories. Thus, the reducing time and heating energy are remarkably reduced.

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 sponge iron from powdered iron oxide, and particularly to a method in which powdered iron oxide is placed in a refractory container (commonly called sagar) and indirectly heated in a so-called tunnel furnace. It is about.

[0002]

2. Description of the Related Art In general, sponge iron is described in "Handbook of Metals, Revision 4".
As shown in Fig. 1 (page 2 in this specification) on page 1363 of "Version" (Maruzen), powdery iron oxide 2 such as mill scale or iron ore powder, which is the main raw material, is mixed with coke, char, etc. as a reducing agent 3. It is filled in the same refractory container 1 in a state separated from the above, and indirectly heated from the outside of the container 1 using a tunnel furnace to reduce and sinter powdery iron oxide.

By the way, as shown in FIG. 2, the main raw material and the reducing agent 3 are filled with the powdery iron oxide 2 in a ring shape in the cylindrical refractory container 1 and the reducing agent 3 is filled with the ring. Are filled in the upper and lower parts, the central part and the outer peripheral part of the container 1 so as to surround the container. Therefore, when this container 1 is heated after filling the raw materials,
In the reducing agent layer, carbon in the reducing agent 3 reacts according to the following equation to generate C
Generates O gas.

C + CO ₂ → 2CO The CO gas generated there diffuses from the reducing agent 3 layer to the raw material layer, and when it reaches the iron oxide layer, a reaction of FeO _n + nCO → Fe + nCO ₂ occurs, As powdery iron oxide 2 is reduced,
CO ₂ gas is produced. This CO ₂ gas is powdery iron oxide 2
The layer diffuses and reaches the reducing agent 3 layer again, in which carbon is changed to CO gas.

By repeating these reactions within a certain period of time, all the powdery iron oxide 2 filled in the refractory container 1 is reduced, and at the same time with the reduction, sintering of the reduced irons progresses. It becomes a sponge iron sintered body in the shape of a cylinder. However, in the above-mentioned conventional technique, diffusion of CO gas and CO ₂ gas in the powdery iron oxide 2 layer and the reducing agent 3 layer determines the progress of the reduction reaction. In particular, in the packed state shown in FIG. 2, since the powdery iron oxide 2 layer and the powdery reducing agent 3 layer are separated, the diffusion distance of CO gas and CO ₂ gas is long and necessary for reduction. Long heating time. For example, in a manufacturing process on an industrial production scale that uses a tunnel furnace for heating, it takes several days from the filling of raw materials to the withdrawal of products, not only the productivity is low, but also the consumption of heating energy required for reduction is significantly large. There was a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method for producing sponge iron having a short heating time required for reduction, a small heating energy, and a low production cost. Has an aim.

[0007]

In order to achieve the above object, the inventor has conducted a number of experiments on shortening the diffusion distance of CO gas and CO ₂ gas and separating iron powder and reducing agent after reduction. The study was repeated. The present invention was made based on the results of these experiments, in which a powdered iron oxide and a powdery reducing agent are filled in a refractory container, and the iron oxide is reduced by indirect heating from the outside of the refractory container. In the method for producing sponge iron by sintering, the powdery iron oxide and the powdery reducing agent are mixed in advance and then filled in the refractory container. Further, regarding the concrete implementation of the present invention, the method for producing sponge iron according to claim 1, wherein the indirect heating means is a tunnel furnace.

[0008]

In the present invention, the powdery iron oxide such as mill scale or iron ore and the powdery reducing agent such as coke powder or char are mixed in advance and then filled in the refractory container. The diffusion distances of CO ₂ gas and CO ₂ gas can be shortened until they become almost equal to the respective particle diameters. As a result, the progress of the reduction reaction due to the diffusion of gas was dramatically accelerated, and the reduction time could be shortened significantly. Furthermore, the production efficiency in the production of sponge iron has been improved, and the production cost can be reduced.

The sponge iron produced by applying the present invention was a porous sintered body obtained by mixing with a reducing agent or its ash and then sintering it. Highly pure reduced powder was obtained.

[0010]

The contents of the present invention will be described below with reference to FIG. FIG. 1 is a diagram showing a raw material filling state in one embodiment of the present invention. The powdery iron oxide 2 as the main raw material is a mill scale crushed to a particle size of 150 microns or less. The powdery reducing agent 3 is a coke breeze having a particle size of 200 microns or less.

First, the mill scale 2 and the coke breeze 3 were mixed in equal weight ratios, and then uniformly filled in a cylindrical refractory container 1. Then, the filling was covered with a disc-shaped refractory lid 4 to complete the preparation for heating. As a comparative example, a container having the filling structure shown in FIG. 1 was prepared. In this comparative example and the example, the mill scale 2 and the coke breeze 3 have the same weight.

Next, the refractory container 1 filled with two kinds of the above raw materials was placed on a truck and passed through a tunnel furnace to heat and reduce the mill scale 2. The tunnel furnace used had a total furnace length of 100 m, and the region of the central portion 40 m was gas-heated so that the atmospheric temperature was maintained at 1150 ° C. Further, the trolley speed of the truck was adjusted so that the target reduction rate of sponge iron after the blast furnace was 98.0%. That is, since the temperature range of 1150 ° C. is constant at 40 m, the passing speed of the trolley is adjusted by adjusting the time of holding at 1150 ° C.

The results of operation under such conditions are summarized in Table 1.

[0014]

[Table 1]

As is clear from Table 1, in this embodiment,
The truck speed was 1.5 m / hr, which was 26% faster than the conventional example of 1.1 m / hr. This means that, as described above, the sponge irons produced in this example and the conventional example have the same weight, so that the productivity per unit time is improved by 26%. Along with this, the amount of heat required to heat the sponge iron per unit weight is 2730 Mcal / ton to 2
It was possible to reduce it to 100 Mcal / ton by about 30%.

[0016]

According to the present invention, reduction time and heating energy can be significantly reduced in the sponge iron manufacturing process using a tunnel furnace rather than powdered iron oxide.

[Brief description of drawings]

FIG. 1 is a diagram showing a raw material filling state in a cylindrical refractory container when the present invention is applied.

FIG. 2 is a view showing a raw material filling state into a cylindrical refractory container according to a conventional method.

[Explanation of symbols]

 1 Cylindrical refractory container (container) 2 Powdered iron oxide (mill scale) 3 Powdered reducing agent (coke breeze) 4 Refractory lid

Claims (2)

[Claims] 1. A sponge iron is manufactured by filling a powdered iron oxide and a powdery reducing agent into a refractory container, and indirectly heating from the outside of the refractory container to reduce and sinter the iron oxide. In the method, the sponge iron is produced by previously mixing the powdery iron oxide and the powdery reducing agent and then filling the refractory container. 2. The method for producing sponge iron according to claim 1, wherein the indirect heating means is a tunnel furnace.