JPH03257109A - Method for treating by-product produced in smelting reduction process - Google Patents

Abstract

PURPOSE:To effectively treat by-product while lowering T.Fe concn. in slag and obtaining molten metal by executing electrially conducted heating treatment while adding carbonaceous material to the by-product having the specific T.Fe concn., which is obtd. by adjusting bottom blow gas blowing quantity. CONSTITUTION:In a metallurgical furnace A, which can blow gas from the top, oxygen is top-blown from a lance 1 and smelting reduction is executed to iron raw material containing iron oxide charged together with the carbona ceous material and flux. At this time, the bottom blow gas is adjusted and temp. of molten metal 5 is made to 1360-1450 deg.C. By this method, T.Fe concn. in the produced slag 3 is made in the range of 3-9%. This by-product slag 3 is discharged and by using electrodes 9 in a vessel B, the electricity is conducted to heat the molten metal. At this time, it is desirable that dust by- product in the above smelting reduction process is further blown together with the bulky carbonaceous material 10. By this method, the slag 8 of <=2% of T.Fe concn. and the molten metal 14 are produced from the above slag 3.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention aims to eliminate by-products, ie, slag, which have been a hindrance to the practical application of the smelting reduction method, which is expected to solve the problems of the current blast furnace method. environmentally friendly,
It also relates to a method for making it possible to use it effectively as a resource.

(Prior technology) The blast furnace method, which is currently the main iron-making process, has excellent characteristics as a method for producing hot metal in large quantities, but it has low production elasticity, and in order to increase the efficiency of the blast furnace, it is difficult to burn ore. It is necessary to coke a special coking coal as coal, and the hot metal produced by this method is enriched with almost all the phosphorus brought in from the raw material; Problems include the high cost of removing phosphorus in the post-process. The smelting reduction method is being researched as a method to solve these drawbacks.

In the method of the present invention, which is one of the smelting reduction methods and uses an apparatus capable of top-bottom blowing, there is no need to subject the ore to agglomeration treatment such as sintering, and it is possible to use coking coal as the carbon material. It is expected to be a method that can solve the problems inherent in the blast furnace method, such as not requiring special equipment, quick start/stop operation, and high production flexibility, and unlike the blast furnace method, dephosphorization is possible. and is being actively researched.

However, the treatment of by-products, which is one of the problems of the melt reduction method, has not yet been solved. The first and most problematic by-product is slag. One of the characteristics of the smelting reduction method is that it suppresses the reduction of phosphorus brought in from the raw materials, allowing it to directly produce low-phosphorus metal. However, on the other hand, the slag contains 3% or more of iron oxide as (T, Fe). Slag containing such iron oxide has problems from the viewpoint of slag utilization, such as color, and it is necessary to lower the iron oxide concentration in order to broaden its uses. However, if slag reduction treatment is performed for leverage in the presence of metal, phosphorus reduction will also occur at the same time, making it impossible to demonstrate its special characteristics. On the other hand, if the slag is separated from the metal and subjected to reduction treatment, the heat of the reduction reaction is taken away, the temperature decreases, and the reduction reaction is inhibited.

Another problematic by-product is dust.

The dust contains iron, mainly iron oxide, carbonaceous powder, and sulfur. Approximately 60% of the sulfur content contained in the raw material charged into the smelting-reduction furnace is vaporized, and plays an important role in the S removal reaction in the smelting-reduction furnace.

One possible way to dispose of the dust is to recycle it into a normally operating furnace. It is true that there is no problem in recycling the iron and carbonaceous materials, but on the other hand, the 8% that has been vaporized and removed will be returned, causing the problem of raising the S level of the metal.

As mentioned above, if slag and dust, which are by-products of the melting reduction process, are treated in a manner that is normally considered to be
This results in an increase in S, making it impossible to take advantage of the refining characteristics of the smelting reduction method.

(Problems to be Solved by the Invention) In the present invention, the slag generated by the smelting reduction method is treated to reduce the iron oxide concentration to a level where there is no problem in using it as slag without increasing the phosphorus concentration of the metal. , we are attempting to solve the problem of by-product treatment while making use of the deP and deS functions of smelting reduction by performing dust treatment in a rational manner without particularly returning the metal to S.

(Means for solving the problem) In a metallurgical furnace in which gas is blown from the top to the bottom, an iron raw material containing iron oxide and carbon material are introduced while blowing oxygen from the top to the bottom, and the temperature of the molten metal is raised to 1360 to 1450. ℃ range, and the slag (T, Fe) concentration is 3 to 9%.
Adjust the amount of gas blowing into the bottom blowing crucian carp so that it falls within the range of
After carrying out the first step of producing molten metal and slag, the slag, which was pressurized outside the furnace, is heated with electricity while adding carbonaceous material to produce slag and molten metal with a (T, Fe) concentration of 2% or less. A second step is carried out to obtain . In addition, in this second step, the first
Uses dust generated during the process.

(For writing) FIG. 1 shows an example of equipment used in the first step of the present invention.

This equipment is a metallurgical furnace A capable of top-bottom blowing of gas, and oxygen is supplied through a top-blowing lance 1. Gas bottom blowing is performed to stir the melt, and nitrogen gas is usually used. The raw materials are iron raw materials containing iron oxide such as iron ore or its pre-reduced product, coal or a carbonaceous material prepared by preheating it to adjust the volatile content, and fluxes such as coal. In the figure, 2 is a refractory, 3 is a slag, 4 is a bubble, 5 is a metal bath, and 6 is a carbon material.

The temperature of the melt can be measured, for example, by inserting a sub-lance into the metal layer, but this value is between 1360 and 145.
The feed rate of the iron raw material is adjusted so that the temperature is within the range of 0°C.

If the value exceeds 1450° C., as shown in FIG. 2, the P concentration [P] of the metal cannot be sufficiently reduced, which is not suitable for the purpose of the present invention. On the other hand, if the temperature is less than 1360°C, the operation becomes unstable, which is not preferable.

The iron oxide concentration of the slag, ie (T, Fe), is determined by the balance between the iron oxide supply rate from the iron raw material and the reduction rate of the iron oxide. Since the supply rate of iron oxide is determined by productivity, it is ultimately determined by the reduction rate of (T, Fe), that is, the amount of bottom-blown gas. In the present invention, (T, Fe) is desirably adjusted to 3% or more and 9% or less. This is because, as shown in Figure 3,
This is because if (T, Fe) is less than 3%, the P concentration [P] of the metal cannot be sufficiently reduced. On the other hand, (T, Fe) is 9
If it exceeds %, the rate of wear of the refractory increases rapidly, and in terms of operation, abnormal forming is likely to occur, resulting in instability.

In order to satisfy such conditions regarding the iron oxide concentration of the slag, it is preferable to blow bottom blowing gas in a range of 3 to 15 Nm3/l-metal per unit amount of metal present in the furnace. As a seed, nitrogen gas is the most practical in terms of handling, effectiveness, and cost.

The C concentration of the metal is determined by the relative relationship between the rate of supply of carbon from the carbon material to the metal and the rate of removal of carbon from the metal, that is, the reaction rate of C in the metal and iron oxide or an oxidizing atmosphere.

The rate of carbon supply to the metal (more precisely, the carburization rate) depends on the distribution state of the carbonaceous material and metal within the slag layer. Of these, the distribution of metal depends on the amount of bottom-blown gas. On the other hand, the distribution of carbonaceous material depends on the particle size distribution. The degree of grain refinement of carbonaceous materials when rapidly heated in a furnace is determined by the content of volatile matter contained therein. Therefore, the particle size distribution of the carbon material in the in-furnace slag layer, that is, the rate of carburization into metal, can be adjusted by the volatile content of the coal used.

In the present invention, it is necessary to maintain the C content of the metal at 3% or more. When it is less than 3%, the reduction reaction rate decreases and the slag (
T, Fe) increases, and the previously mentioned (T, Fe) increases by 9%.
The reasons for this are that it becomes difficult to satisfy the following conditions under high productivity conditions, and that the melting point of the metal rises, making it difficult to satisfy the aforementioned low-temperature operating conditions of 1450° C. or lower.

In order for the C concentration of the metal to satisfy these conditions, in the case of large-scale equipment, the carbonaceous material must have a volatile content of 5% or less (for example, coke or char, which is heated outside the furnace to remove volatile content). ) with a carbon content of at least 10
It is necessary to use % or more.

On the other hand, the composition of the slag is adjusted by adding components such as CaOlMgO as a flux to components such as SiO□, AlzOs, and MgO brought in from ores, carbonaceous materials, and the like. The appropriate composition is determined by taking into account the refining ability and operational stability under the above temperature conditions. For example, ((!kcao
)◆nMg0)/ (ksioz)+(96AMzOs
)) is in the range of 1.0 to 1.4.

The slag composition and the amount of slag, or the total amount of dust generated, are factors directly related to blocking the oxygen jet and metal, and have a large influence on suppressing the amount of metal-induced dust generated.

Dust that is caused by metals, that is, dust that has a high iron oxide concentration is not preferable because it increases the amount of power required in the second step of the present invention. In order to reduce the amount of dust generated due to metals, the amount of slag needs to be 340 kg/or more relative to the amount of metal present in the furnace. In order to satisfy this condition, it is necessary to adjust the amount of slag exhaust pressure.

The exhaust gas is removed by a dry or wet dust collector, and the separated dust is sent to processing steps such as drying and molding as necessary.

The metal and slag produced are intermittently or continuously discharged outside the furnace. Slag and metal may be compared separately or at the same time, but in either case they are separated outside the furnace using the difference in specific gravity and placed in a ladle-like container lined with refractory material. .

In the next process, impurities such as carbon are removed from the metal, and it is refined into molten steel. On the other hand, the slag and dust are sent to the vS2 step of the present invention for treatment. Fig.'s4 shows an example of the equipment used in the second step of the present invention.

A carbon or metal electrode 9 is inserted into the molten slag 8 housed in a container 13 lined with refractory material, and electricity is applied to generate heat. The amount of heat generated at this time is used as the heat of the reduction reaction of iron oxide in the slag, and the slag is kept in a molten state while this reduction reaction proceeds until a predetermined (T, Fe) value is reached. The current may be either direct current or alternating current.

Carbon material is used as a reducing agent for iron oxide in the slag. This carbon material may include coal, coke, etc. added in the first step, a portion of the slag that comes out when it is discharged from the furnace in the first step, and various other materials containing carbon. It is possible.

In order to increase the reduction reaction rate by incorporating carbonaceous material whose true specific gravity is smaller than that of the slag into the slag, it is desirable to blow a gas such as nitrogen into the slag layer and stir it. When the carbonaceous material is in powder form, it is also effective to blow the powdered carbonaceous material with gas.

It is appropriate that the amount of carbon material added be 150 to 250% of the carbon material equivalent required to reduce the iron oxide to be reduced in the slag through the CO production reaction. In the figure, 10 is a lump carbon material, 11 is a lance, 12 is a refractory, and 13 is a cover.
14 indicates generated metal, and 15 indicates bubbles.

Since the dust generated in the first step contains carbon, it can be used as an iron oxide reducing agent in the slag. Furthermore, in this case, it is possible to stabilize the sulfur content contained in large amounts in the dust by fixing it in the slag, which is also effective in terms of environmental measures regarding sulfur.

Furthermore, the dust generated in this first step is dried as is if necessary, or is formed into briquettes, etc., and added by blowing method in the case of powder, or by top charging method in the case of molded products.

When the dust is added to the molten slag, the carbon content reacts with iron oxide in the slag to generate a gas containing CO as a main component. This point is the same as normal carbon material. Further, the iron oxide contained in the dust is infiltrated into the molten slag, and then reduced by the added carbonaceous material. Therefore, it is necessary to increase the amount of spreading agent added by the amount of iron oxide contained in the dust that is insufficient due to the carbon content in the dust.

Most of the sulfur content in the dust is melted into the molten slag and fixed. However, if the dust addition conditions are inappropriate, some of the sulfur will migrate back into the dust. In order to reduce this ratio, before adding dust, add another carbon material to the slag to lower the (T, Fe) concentration in the slag to 2% or less, preferably 1% or less. This is desirable.

Between the metal produced by iron oxide reduction and slag,
A thermodynamically determined distribution relationship between phosphorus and sulfur occurs. However, since the amount of metal is overwhelmingly smaller than the amount of slag,
In terms of absolute amounts of phosphorus and sulfur, most of them are fixed within the slag.

In particular, when (T, Fe) of slag is low, (5 of slag
%)/(5% of metal) becomes large, so almost all of the sulfur in the dust, that is, the sulfur generated in the first step, will eventually be stably fixed in the slag.

The generated metal containing phosphorus and carbon initially forms as fine particles, but when the slag layer is stirred, it coalesces and settles, and after processing, it can be collected as metal lumps. This metal is the first
It can be used as part of the iron raw material in the process, or as a temperature control material when decarburizing high carbon metals.

Next, a practical example of processing by-products generated in the melting reduction process according to the present invention will be shown.

(Example) First, as a first step, iron ore was reduced under the following conditions using a converter-like container lined with alumina-carbon bricks as shown in FIG. 1.

(1) Raw materials used: ■Iron ore...T, Fe (Total Fe) J9.8
%.

sto, 2.3%.

■Charcoal material 1 ”-F, C (Fixed Carbon)-
53.1%.

V, M (Volatile Matter) -37.2%
.

Ash -10.3%.

■Charcoal material 2-F, C-73.2%, V, M-2.4%.

Ash = 9.8%.

(preheated to 620℃ outside the furnace) ■Flux: Quicklime (97% as CaO) (2) Blowing conditions: ■Metal (seed water) amount: 70t ■Slag (seed water) ) Amount...26t (-370kg/l
-Metal)■Top-blowing gas amount...Oxygen; 2500ONm
'/hr (constant) ■Bottom blown gas amount...Nitrogen: 900
~1100ON'/hr (・Average 11Nm'/hr-
t metal) ■Iron ore supply amount...supply rate/36.0~
42. Ot/hr.

Total amount - 40, Ot ■Charcoal material supply amount...Charcoal material 1; Supply rate: 19.6 t/
hr.

Total amount -19,6 Carbon material 2: Supply rate -3.9 t/hr.

Total amount - 3.9t ■Flux supply amount...4.2 t/hr, total amount 4.
2t Metal temperature: 1410 to 1440°C As a result, the components of the produced metal and the composition of the slag were as follows.

(1) Metal components, C-3, 9%, Sii, 02%,
Mn-0,21%P-0,020%,S-0,036
%.

(2) Slag composition; Cab-43%, SiO, -29
%, MgO-5,6k.

ARzOl-14%, T, Fe-4.5%.

P-0,52%, S-0,15%.

Next, the slag produced in the first step, that is, the melting reduction step, is received in a ladle lined with alumina bricks, and the second
The process involves inserting two graphite electrodes and applying alternating current.In the first stage, only coke powder is blown into the slag layer, and in the second stage, in addition to the coke powder, the ivy is blown into the slag layer. The dust produced in the first step was molded into briquettes and then poured from above.

The temperature of the slag was measured with a thermocouple, and the applied current was adjusted so that the indicated value was in the range of 1400 to 1435°C.

The operational data at this time is shown below.

(1) Slag conditions before treatment; ■Composition: Same composition as at the end of the first step.

■Temperature; 1450℃ (2) Processing conditions of the first stage; (Time when only coke powder was blown into the slag layer) ■Coke powder blowing conditions: Particle size: 1.2 mm or less Carrier gas = nitrogen gas ■Electrification conditions: ...AC, voltage -2.5V.

Current -12000~2300OA ■Processing time...8 minutes (3) Slag conditions at the end of the first stage; ■Composition; Cab-44%, SiO, s30%, M
gO-6,8% A420a-15%, T, Fe-1,
8%.

P-0,39%, S-0,56% ■Temperature, 1390℃ (4) Processing conditions for the second stage; (Time when task briquettes were added along with coke powder) ■Coke powder blowing conditions...First stage ■Dust briquette addition conditions... [Composition] T, Fe1O, 6%, T, C-39, [
i% [Addition method] Continuously add from above ■Electrical conditions: AC, voltage 2.5V.

Current: -20,000 to 2,500 OA ■Processing time: 14 minutes As a result, the situation at the end of the second stage processing was as follows.

(1) Slag composition; Cab-45%, 5t (h-3
1%.

No. z03-15%, MgO-6,8%, T, Fe-0
,8%.

P-(1,28%, S-0,98% (2) Slag temperature, 1397℃ (3) Generated metal component: C-4,3%, P-0,3
%s-o, oi%.

As described above, as a result of treating the slag and dust generated in the melting reduction process according to the present invention, it is possible to provide effectively usable slag with a low (T, Fe) concentration without adversely affecting the melting reduction process. Tonafuta.

(Effects of the invention) By carrying out the present invention, it becomes possible to process by-products such as slag and dust while taking advantage of the refining characteristics of smelting reduction, and solve some of the problems with the current blast furnace iron manufacturing method. It has a great industrial effect because it can promote the practical application of the melting coupled method, which is expected to solve the problem.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of equipment used in the first step of the present invention, FIG. 2 is a diagram showing the influence of metal temperature on the P concentration of metal in the first step of the present invention, and FIG. 3 is a diagram showing the influence of metal temperature on the P concentration of the metal in the first step of the present invention. FIG. 4 is a diagram showing the influence of the (T, Fe) concentration of iron oxide in the slag on the P concentration of the metal in the first step of the present invention, and FIG. 4 is a diagram showing an example of the equipment used in the second step of the present invention. . 1...Lance, 3 River slag, 5...Metal ¥valley, 7...Lining refractory, 9...Electrode, 11...Lance, 13...Cover 15...Bubble, A ...Metallurgical furnace, 2...Refractory, 4...Bubble, 6...Charcoal material 8...Slag, 10...Lumpy carbon material, 12...Refractory, 14... Generated metal, B...container. To Figure 1 Figure 4 Ma C-ma\ Bobble l5CL, Z

Claims (1)

[Claims] 1. In a metallurgical furnace capable of blowing gas from the top and bottom, an iron raw material containing iron oxide and carbonaceous material are charged while blowing oxygen from the top, and the temperature of the molten metal is in the range of 1360 to 1450°C. Further, the (T.Fe) concentration of the slag is adjusted to 3.
After the first step of producing molten metal and slag by adjusting the amount of bottom-blown gas in the range of ~9%, carbonaceous material is added to the slag discharged outside the furnace while heating it with electricity. A method for treating by-products generated in a melting reduction step, comprising: carrying out a second step of obtaining slag and molten metal having a (T.Fe) concentration of 2% or less. 2. In the second step, the carbonaceous material added while heating the slag with electricity partially contains the dust generated in the first step. Processing method.