JPH02153011A - Smelting reduction furnace - Google Patents

Abstract

PURPOSE:To make eroding speed of the whole lining in a furnace uniform by using carbon-bonding graphite-containing neutral brick below molten slag surface and ceramic-bonding basic brick above the molten slag surface in the lining structure of the smelting reduction furnace. CONSTITUTION:The iron ore is supplied into the smelting reduction furnace A together with reducing agent and slag making agent, and oxygen is blown into the furnace from a top blowing lance L and bottom blowing nozzles N, etc., and the smelting reduction is executed to the above iron ore to obtain pig iron. In the above smelting reduction furnace, the furnace wall part lining positioned below the molten slag S surface under operation is constituted of the carbon-bonding graphite-containing neutral brick 2. On the other hand, the furnace wall lining above the molten slag S surface is constituted of the ceramic-bonding basic brick 1. The above carbon-bonding graphite-containing neutral brick 2 is desirable to be composition containing 75-90wt.% Al2O3, 7-22% C, 1-5% Al or Si and if necessary, further containing 5-15% SiC. By this method, the eroding speed of the whole furnace lining is uniformized and the service life of the furnace lining is extended and the furnace lining cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a smelting reduction furnace for producing pig iron by melting and reducing iron ore using a rotary furnace.

[Prior Art] In recent years, a technology has been developed for melting and reducing iron ore using, for example, a converter-type rotary furnace.

The manufacturing process generally involves charging seed water in advance, charging iron ore into a furnace together with coke as a reducing agent, anthracite, coal as a slag forming agent, etc., and then blowing oxygen to reduce the iron ore. is known for.

As is already well known, this process is based on the top-bottom blowing converter steelmaking method, and the lining refractories of the smelting reduction furnace are Mg0-C and Mg, which have a good track record of being used in conventional converters.
O-Ca0-C%MgO-MgCO3, CaC03-C
Carbon-bonded graphite-containing basic refractories such as these are often used. These refractories have excellent corrosion resistance against slag with a relatively wide range of basicity (CaO/5iOz), and by enriching MgO in the slag, the amount of erosion loss can be roughly reduced. In addition, it has excellent thermal shock resistance and exhibits high durability in converters. However, it is difficult to say that it is sufficiently suitable as a refractory for a smelting reduction furnace.

[Problems to be Solved by the Invention] As mentioned above, carbon bonded graphite-containing basic refractories exhibit extremely excellent properties in converters that have a relatively high basicity and can be operated at <Mg0k. Reduction furnaces have the following problems.

To explain the reduction of iron ore in detail, iron ore forms a mixed layer with coke, anthracite coal, and slag-forming agent on the surface of the seed metal, and is preheated and melted by the combustion heat of the coke and anthracite coal caused by top-blown oxygen. The molten iron ore is further converted to Fe2O3+3Cc32[Fe]+3(:O
It is reduced by the reaction of The generated CO reacts with top-blown oxygen, resulting in an exothermic reaction of 2CO+023H:(h) in the furnace.

Therefore, the upper part of the slag bath surface has a high temperature and an oxidizing atmosphere.

The slag composition of the slag bath is adjusted to a slag basicity (CaO/510z) of 1.0 to 1.3 in order to increase the reduction rate, and the Al2O3 and MgO concentrations vary slightly depending on the type of iron ore and carbonaceous material. They are around 20% and 5%, respectively.

Under these conditions, when lining with a conventional carbon bonded graphite-containing basic refractory such as Mg0-C, the slag bath and the lining bricks below the slag bath surface are made of high AlxO with low basicity.
s Contact with low MgO slag.

In general, basic bricks containing MgO as a main component are more resistant to low basicity slag than monticerite (CaO/MgO/S).
It produces low melting point minerals such as iOx) and is eroded.

In addition, the amount of MgO dissolved in the slag in the brick is Cab-
5in2-8! It is controlled by the MgO saturation dissolved concentration of the four components 205-Mg0. That is, basicity ([:aO/5
When LO21 is kept constant, as the AlzOs concentration increases, the dissolved MgO concentration increases and the elution of MgO in the brick increases. In order to reduce the concentration of MgO eluted into slag, there is a method of suppressing the amount of eluted MgO by enriching the slag with MgO sources such as dolomite. Increase in amount is not desirable (
The hydration reaction of MgO has an extremely low reaction rate compared to the hydration reaction of CaQ, and there is a high possibility that the concrete structure will break several years after construction, so MgO is severely restricted. Therefore, the generation of high MgO slag poses a problem in terms of resource utilization. ) In the current ironmaking method, the blast furnace method, the slag produced is effectively used mainly as roadbed material and cement raw material.

The smelting reduction method aims to replace the blast furnace as an ironmaking method, and if the produced slag contains a large amount of MgO, the following two problems will occur.

(a) If the MgO content is close to the saturation level, it is undesirable as a roadbed material because it tends to be digested.

(b) If it contains 7% or more of MgO, it becomes unsuitable as a raw material for cement. Therefore, in order to effectively utilize the generated slag in the route of the current blast furnace method, it is necessary to
It is not possible to increase the gO content. Therefore, in situations where enrichment of MgO in slag is not possible due to these reasons, Mg076%, which has shown high durability in conventional converters, cannot be used.
In the case where the inner lining is made of Mg0-C bricks with a C1% content, the elution of MgO in the bricks determines the rate of erosion.

Under blast furnace operation, the erosion rate of this part is 0.04++m
/ acid blowing time (++in) and the amount of erosion is 4.8 per heat.
01111, and when the lining layer thickness is 600 mm, the furnace stops after 120 heats, and the erosion rate is approximately 4 times larger than the o, otmm/oxygen blowing time (ffIin) in the case of a conventional converter. .

On the other hand, at the upper part of the slag bath surface, a high-temperature oxidizing atmosphere is created by the above-mentioned reduction product gas CO2 and 02 gas blown into the upper part, and on the operating surface of the MgO-[: brick, preferential oxidation of graphite causes a significant decrease in strength, leading to erosion. The speed becomes as high as 0.2 mm/acid blowing time (min).

As a countermeasure to this problem, attempts have been made to improve the oxidation resistance by adding metals such as octamata, St, etc. and oxidizing them preferentially, but no drastic improvement has been achieved.

The present invention has been made in order to provide a smelting reduction furnace having a lining structure highly suitable for smelting and reducing iron ore.

[Means for Solving the Problems] The present invention provides iron ore into a furnace together with a reducing agent and a slag-forming agent,
In a smelting reduction furnace that produces pig iron by smelting and reducing iron ore by blowing oxygen into the furnace, the lining of the furnace wall and bottom of the furnace located below the slag bath surface is covered with carbon bonded graphite. This smelting reduction furnace is constructed of neutral bricks, and the lining of the side wall located above the slag bath surface during operation is constructed of ceramic bonded basic bricks with a high melting point.

The present inventors first conducted experiments to elucidate the in-furnace conditions for high-temperature oxidized gas refractories above the slag bath surface, and found that
It was confirmed that ceramic bonded oxide refractories exhibit high durability. Specifically AJ! 20s-5lo2 refractories soften at high temperatures in the relevant parts, so they are stable against oxidation but have low corrosion resistance.

Mg0-Grt03. Basic refractories that form direct bond ceramic bonds, such as MgO-MgO.AJhOs, have shown high durability. In a fixed type smelting reduction furnace, the area above the slag bath surface is not constantly immersed in molten slag or molten metal, and splashes, etc. only adhere to the surface of the bricks, passing through the pores in the bricks and melting the slag or molten metal. Since the metal does not penetrate, there is no formation of a dense altered layer on the working surface side, and there is almost no structural spalling, which is a drawback of ceramic bonded basic refractories.

On the other hand, damage caused by thermal shock can be dealt with by strengthening heat retention to minimize temperature fluctuations between operations. There is no tissue deterioration due to oxidation of
Shows high durability above the slag bath surface.

In addition, the refractories in the parts of the lower part of the slag bath that are immersed in the low basicity, high^12's, low MgO slag are based on AQ20s aggregate, which has a lower diffusion rate than MgO to the slag, to prevent slag infiltration. It contains graphite that prevents heat shock and improves thermal shock resistance, and further contains A2, St alone or two
f! It was confirmed that if carbon-bonded graphite-containing neutral bricks were used to prevent the oxidation of graphite, the elution of aggregate would be significantly alleviated and high durability would be achieved. In addition, Al2O
Although the melting point is lower than that of 5, the solubility of the relevant part is at most 15.
Since the temperature is around 00°C, there is no adverse effect due to softening of the aggregate.

Therefore, in the smelting reduction furnace of the present invention, the bricks constituting the lining below the slag bath surface and the bricks constituting the lining above the slag bath surface are made of bricks with different properties, so that the suitability of each brick can be fully maximized. This is what I did.

The graphite-containing neutral refractories of this carbon bond include:
Afi, o, -c system, 1zOs-3iC-C system is suitable, and in the case of AR20s-C system, weight% "t'ALO
Contains s75% to 90%, C7 to 22%, and further A2,
When 1 to 5% of Sl, etc. is contained as an oxidation inhibitor of graphite, it is suitable for ensuring slag resistance, oxidation resistance, and thermal shock resistance.
Weight%: 8u2o3 5-90%, C5-20%, S
A material containing 5 to 15% of iC and 1 to 5% of a metal such as A4, St, etc. as a graphite oxidation inhibitor is suitable for ensuring slag resistance, oxidation resistance, and thermal shock resistance.

Note that the SlC in this case vitrifies under operating conditions and coats the brick surface, particularly suppressing oxidation of graphite and improving spalling resistance.

In addition, it is preferable to use Al2O3, SIC, C, etc. with a purity of 96% or higher in order to suppress the reaction with slag.
, when using Ca1-Al1 equilateral alloy, 8g%C
The content of a is about 2%, but since 1g% Ca has many negative elements, it is preferable to keep it to 2% or less as much as possible.

[Example] Embodiments of the present invention will be described below with reference to FIG.

The melting reduction furnace in this example has a capacity of 17 Qton/ch.
This is a converter-type smelting reduction furnace with a furnace capacity of .

In Figure 1, A is a smelting reduction furnace, and inside the furnace is a molten metal bath M.
It is roughly divided into the iron ore, coke, slag, mixed bath area S, and the upper atmosphere area.

The furnace wall in the upper atmosphere zone B is lined with MgO-Cr2O* direct bond bricks 1, which are ceramic bond basic bricks, and carbon bond graphite-containing neutral bricks 2 of N20s-9iC-C are lined in the other parts. Uchihari Sushita. In addition,
In the figure, the top blow lance N is a bottom blow nozzle.

Here, the results of laboratory tests on the compositional characteristics of each of the bricks used are shown in Table 1, together with the conventional Mg0-C type bricks.

Table-1 *■CaO/5iOz= 1.0, ^JhOs-20%
, the t8 loss was calculated by immersing it in MgO-5% slag at 1600°C x 511r.

*■1B00℃xllllr oxidation test under atmospheric atmosphere to calculate the decarburized layer thickness.

The characteristic feature is basicity of 1.0. AlzOs 20%
, the erosiveness of slag equivalent to smelting reduction of 05% Mg is as follows:
A120s-C-^i, o3-slc-c > MgO
-Cr2O5 direct bond>Mg0-C, ^2. In the case of O5-based materials, the elution rate into the slag is low, and the oxidation loss of graphite-containing bricks is significant under high-temperature oxidizing atmosphere.

Table 2 compares the erosion rate when one charge of smelting-reduction reaction is completed in about 2 hours in the aforementioned converter-type smelting-reduction furnace with a furnace capacity of 170 ton/ch compared to that of a conventional lining structure.
Compared to the conventional method, the corrosion rate of the furnace wall above the slag bath surface is 1/16, and that below the slag bath surface is 1/2.4.
This greatly improves the lining life, which significantly reduces the unit consumption of furnace materials, improves productivity, and significantly reduces manufacturing costs.

Table 2 Although the examples of AlxOz-G bricks were not described in detail, the same erosion rate as A1203-5IC-C in Table 1 can be obtained. In addition, Al, O, -C1 octagonal 20.
-5iC-C. For example, in the case of A2, metals such as kQ and St form Affi4Cs with C in bricks,
It is effective in suppressing the oxidation of graphite and developing strength in the graphite matrix portion.

In addition, in the present invention, in order to prevent spalling due to rapid cooling of the lining bricks due to heat radiation from the furnace mouth between operations, heat retention was strengthened compared to the conventional case where the lining was made of Mg0-C bricks. .

[Effects of the invention] In the smelting reduction furnace of the present invention, the lining relining structure is such that the high temperature oxidizing atmosphere part above the slag bath surface is lined with ceramic bond basic refractory, and the other parts are lined with carbon bond graphite. By lining the furnace with neutral bricks, the loss rate of the lining of the entire furnace becomes uniform, and the life of the furnace can be significantly extended and the cost of furnace materials can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal cross-sectional view showing one embodiment of the melting reduction furnace of the present invention. 1... Ceramic bond basic brick, 2... Carbon bond graphite-containing neutral brick, B... Atmosphere region,
S... Top blowing lance, M... Molten metal bath,
N...bottom blowing nozzle, S...slag bath for iron ore, coke, anthracite, and slag pipes. Agent Teruo Taniyama and 4 others

Claims (1)

[Claims] 1. Supplying iron ore together with a reducing agent and a slag-forming agent into a furnace,
In this smelting reduction furnace, which produces pig iron by melting and reducing iron ore by blowing oxygen into the furnace, the lining of the furnace wall, which is located below the molten slag surface during operation, is made of carbon-bonded graphite-containing neutral bricks. A smelting reduction furnace 2 characterized in that the lining of the furnace wall located above the slag bath surface in the operating state is composed of ceramic bonded basic bricks. Al_2O_3 is 75-90% by weight, C=7-22
%, and further contains 1 to 5% of one or two types of Al and Si, and is made of a carbon bond graphite-containing neutral brick. Furnace 3 Under operating conditions, the lining of the furnace wall located below the slag bath surface is 75 to 90% by weight of Al_2O_3 and C=7 to 2.
2%, SiC in the range of 5 to 15%, and a carbon bond graphite-containing neutral brick containing 1 to 5% of one or both of Al and Si. The melting reduction furnace according to claim 1, characterized in that