JPH01195223A - Molten iron gutter type smelting reduction iron manufacture method - Google Patents

Abstract

PURPOSE:To make an operation smooth and to enhance efficiency by controlling the viscosity of by-produced slag in a process for feeding an iron manufacturing raw material to the molten iron on the molten iron gutter of a pig iron producer to reduce it. CONSTITUTION:An iron manufacturing raw material is fed to molten iron M on the molten iron gutter of a pig iron manufacturing facility through an iron manufacturing raw material blowing pipe 6. Further carbon material is blown through a carbon material blowing pipe 8 and oxygen is blown through an oxygen blowing pipe 7. Iron oxide component incorporated in the iron manufacturing raw material is melted and reduced. Dischargeability of slag S is made good by controlling the viscosity of slag S by-produced in this reducing process and the so-called iron flow wherein molten iron M is discharged together with slag S is inhibited.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention utilizes the retained heat of hot metal flowing out from a pig iron manufacturing equipment through a hot metal trough as a heat source, and utilizes carbon in the hot metal as a reducing agent. Furthermore, regarding the improvement of the method of making iron by melting and reducing iron ore, pre-reduced iron ore, scrap, and other raw materials for steelmaking by adding carbonaceous materials, in particular, it is possible to improve the method of making steel by melting and reducing iron ore, pre-reduced iron ore, scrap, etc. By appropriately controlling the viscosity, the slag removal performance can be adjusted,
In addition, by suppressing the amount of flow pig iron per unit amount of slag discharged (the amount of hot metal taken into slag and discharged, i.e. iron loss), productivity and operational stability can be increased. It concerns the reduction iron manufacturing method.

[Conventional technology] Steel manufacturing methods are broadly divided into indirect iron manufacturing methods, represented by the blast furnace method, and direct iron manufacturing methods, represented by the smelting reduction method.Currently, the blast furnace method, which allows continuous operation and is suitable for mass production, is the mainstream. It becomes.

However, the blast furnace method requires enormous construction and maintenance costs, and since it uses a vertical moving bed reaction, it is necessary to use a method that acts as a reducing agent in order to improve operational efficiency and stability. The coke to be used and iron ore, which is the iron source, must be adjusted to have appropriate size and crushing strength, and it takes a great deal of effort and cost to adjust the charging raw materials.

On the other hand, the smelting reduction method does not require large blast furnace equipment, and since it is a method that reduces iron ore and other raw materials for iron making in a molten state, it can be used even with relatively low-grade coal or powdered iron ore. It can be used with stones, etc. without any problems, and it has the advantage of higher reaction rate and reaction efficiency than the blast furnace method, which mainly involves a reduction reaction between solids and gases. has been done.

[Problems to be Solved by the Invention] Smelting reduction ironmaking methods are classified according to the type of furnace used, and typical methods include methods using a rotary furnace, methods using a converter type iron bath furnace, and coke-filled method. There are three methods using a vertical furnace, but the common problem with these methods is that they cannot continuously tap the hot water and tap the slag, resulting in low productivity. In other words, in all of these methods, melting and reduction is carried out in a batch manner, and tapping and slaging are performed intermittently, for example, every 1 to 2 hours, so compared to continuous methods using a blast furnace, the tapping and slag operations are shorter. Not only are these post-processing operations troublesome, but the thermal efficiency of the post-processing furnace is low as it is cooled each time, and in order to increase productivity, it is necessary to store a certain amount of hot metal and slag in the furnace. Therefore, rather large blast furnace equipment is required.

Under these circumstances, the present inventors conducted research with the aim of developing a steel manufacturing method that is economical in terms of both equipment costs and operating costs, and that is continuous and highly productive. One of the results of this research is that the heat source is the hot metal flowing through the hot metal gutter in the pig iron manufacturing equipment (hereinafter simply referred to as pig iron manufacturing equipment) such as blast furnaces, Chievola or smelting reduction iron making equipment, and the We developed a molten reduction method for making iron by melting and reducing raw materials for iron making using carbon as a reducing agent, and filed a patent application earlier (Japanese Patent Application No. 186,400/1986, unpublished).

In other words, this method injects ironmaking raw materials into hot metal flowing through hot metal sluices, uses the retained heat of the hot metal as a heat source, uses carbon contained in the hot metal as the main reducing agent, and further reduces the amount of reducing agent and heat that is insufficient. This method involves injecting ironmaking raw materials into hot metal to perform smelting reduction while supplying carbonaceous materials and combustion oxygen to compensate for the ■Equipment can be significantly downsized; ■Silicon and manganese contained in the hot metal are also used as reducing agents, so the consumption of reducing agents is small, and the heat retained in the hot metal is also effectively used, increasing thermal efficiency. It has many features such as: (1) hot metal produced by melt reduction and by-product slag are efficiently separated and discharged on the downstream side, so post-processing is good.

For example, FIG. 1 is a schematic vertical cross-sectional explanatory diagram showing an embodiment of the invention of the prior application, in which 1 is a smelting reduction iron making device installed in the middle of a hot metal gutter in iron making equipment such as a blast furnace, and 2 is a smelting reduction iron making device installed in the middle of a hot metal gutter in iron making equipment such as a blast furnace. A lid for covering the upper part of the apparatus 1 to prevent heat dissipation, 3 a slag drain, 4 a submerged weir, 5 an overflow weir, 6 a steelmaking raw material blowing pipe, 7 an oxygen blowing pipe, and 8 a Carbon material injection pipe, 9 is exhaust gas duct, 10 is hot metal pot, M is hot metal, S is slag
, C indicate carbon materials, respectively.

Among the hot metal and slag discharged from iron making equipment such as a blast furnace, slag with a low specific gravity is separated and removed at an appropriate location upstream upstream to the illustrated smelting reduction iron making apparatus 1. Then, a slightly deeper retention portion is provided in the hot metal trough at a suitable location on the downstream side, thereby forming the iron making apparatus 1 as shown in the figure. That is, this iron making apparatus 1 has a lid body 2 provided for preventing heat radiation, and a steel making raw material blowing pipe 6, an oxygen blowing pipe, a carbon material blowing pipe 8, and an exhaust gas duct 9 are attached to the lid body 2 provided for preventing heat radiation. From the injection pipe 6, iron-containing raw materials such as iron ore, pre-reduced ore, scrap, etc. and auxiliary materials such as quicklime are injected deep into the hot metal M at appropriate ratios, and from the carbon material injection pipe 8, powdered charcoal is injected. Material C is blown in, and at the same time oxygen (or air) is blown in from the oxygen blowing pipe. Then, the ironmaking raw material injected into the hot metal M is melted by the retained heat of the hot metal M and the combustion heat of the carbon material, and the iron oxide components in the ironmaking raw material are dissolved in the hot metal M while floating in the hot metal M. Most of the iron is reduced through a transitory reaction with the iron, which is contained in a large amount, and is further reduced by reacting with the injected carbonaceous material or carbon monoxide generated by its combustion, and the generated reduced iron is added to the hot metal M. After being taken in, the water passes through the lower part of the submerged weir 4, overcomes the overflow weir 5, and flows downstream. On the other hand, gangue components such as silica, alumina, and titania contained in raw materials for steelmaking form a slag together with slag-forming agents such as quicklime that are injected at the same time, but since these have a smaller specific gravity than hot metal M, they do not form on the surface of hot metal M. The slag floats to the surface and is sequentially separated and discharged from the slag 3. The exhaust gas generated during this time is extracted from the exhaust gas duct 9.

For example, the method of the prior invention is configured as described above, but in order to smoothly proceed with such ironmaking operations, it is important to know how to effectively separate the by-product slag from the hot metal and make it flow out into the 3 directions of the slag drain. It is extremely important to decide what to do.

However, the viscosity of slag S produced in this melt reduction process is about 50 to 150 times that of hot metal M, and its fluidity is poor.Furthermore, the fluidity varies markedly depending on the slag temperature and slag composition, so it is difficult to control the operating conditions. A slight fluctuation may increase the slag S's viscosity and deteriorate its fluidity, resulting in poor flow in the three directions of the slag drainage gutter, or in the worst case scenario, the slag may stagnate, resulting in the inability to operate.

Moreover, as the viscosity of the slag S increases, the hot metal M that adheres to the surface of the slag S and mixes into the slag mass becomes difficult to separate and is ejected together with the slag S (this phenomenon is referred to as flow iron in this specification). ), which is a major cause of lower iron yield.

Moreover, when the slag viscosity increases and the slag removal performance deteriorates, it must be scraped out manually, but in this case, the highly viscous slag must be forcibly removed from the hot water surface.
Hot metal may be directly scraped up and discharged, further increasing the amount of flowing pig iron.

The present invention has been made in view of these circumstances, and its purpose is to facilitate the separation and discharge of slag when carrying out the hot metal gutter type smelting reduction ironmaking method as described above, and to The purpose of this invention is to provide a method that minimizes iron loss due to flow pig iron and allows iron manufacturing operations to be carried out smoothly with excellent productivity and workability.

[Means for Solving the Problems] The configuration of the iron-making method of the present invention that can solve the above-mentioned problems is such that the iron-making raw material, carbon material, and oxygen are supplied to the hot metal on the hot metal gutter in the pig iron manufacturing equipment. The gist of this method is to melt and reduce the iron oxide component therein, and to adjust the slag removal properties by adjusting the viscosity of the slag that is produced as a by-product in the melting and reduction process. In this case, if the viscosity of the produced slag is maintained at 10 poise or less, flow iron flow during slag discharge can be suppressed, and the iron reduction yield can be maintained at a high level.

[Function] A feature of the present invention is that, when carrying out the hot metal sluice-type smelting reduction ironmaking process as shown in FIG. The iron content loss can be reduced by adjusting the properties or by suppressing flow iron during slag discharge. In other words, in the hot metal trough type smelting reduction ironmaking process, iron oxide components contained in the ironmaking raw materials are continuously smelted and reduced by supplying ironmaking raw materials, carbonaceous materials, and oxygen to the hot metal flowing out from the pig iron manufacturing equipment as described above. At the same time, a large amount of slag is produced in the system. Therefore, in order to carry out this ironmaking operation smoothly, the by-product slag must be separated from the hot metal and discharged from the system each time, but the separation and discharge of slag is also shown in Figure 1. Generally, the slag is drained through a slag drain, and in order to smoothly drain the slag, it is most effective to appropriately adjust the viscosity of the by-product slag to control its fluidity. In this case, if the operating conditions are controlled so that the viscosity of the by-product slag is 10 poise or less, more preferably 5 poise or less, the separation of hot metal and slag will be performed smoothly, flow pig iron will be suppressed, and iron loss will be reduced. It was confirmed that this could be suppressed to a minimum.

Incidentally, Figure 2 shows the viscosity of by-product slag and slag waste when iron ore and quicklime are used as raw materials for iron making, and the hot metal gutter type smelting reduction ironmaking method is carried out in accordance with the method shown in Figure 1. The relationship between speed and its variation is shown, and the third
The figure is an experimental graph showing the relationship between the viscosity of by-product slag and the amount of flow per unit of slag discharged. As is clear from Fig. 2, when the slag viscosity is 10 voids or less, more preferably 5 voids or less, the amount of fluctuation in the slag removal speed is small and the sludge removal speed itself is large, and the slag removal is smooth. It will be held in However, when the slag viscosity exceeds 1° void, the slag removal speed becomes extremely slow, and the slag becomes viscous and lump-like and is intermittently and irregularly removed, causing fluctuations in the slag removal speed. The amount will also increase rapidly. If this condition progresses further, natural drainage by the flow of the slag itself becomes impossible, and manual forced scraping becomes necessary.

Furthermore, from Fig. 3, it is possible to suppress the flow rate to a low level by suppressing the slag viscosity to 10 voids or less, more preferably 5 voids or less, and if it exceeds 10 voids, the iron loss due to flow increases significantly. I understand.

In this way, the viscosity of slag is closely related to its drainage properties and iron loss due to flow theory, but the viscosity of slag changes depending on the temperature and composition of the slag (basicity, iron oxide concentration, etc.) Therefore, in actual operation, it is recommended to control the operating conditions by the following method and adjust the slag viscosity to an appropriate level.

(i) Increase in slag temperature Increasing the temperature of varnish slag lowers its viscosity and increases its fluidity. The slag fluidity is improved by increasing the slag temperature by increasing the preheating temperature and by increasing the amount of oxygen blown to increase the secondary combustion rate of the reducing gas.

(ii) Adjustment of iron oxide content in slag As the content of iron oxide in slag increases, the viscosity decreases and fluidity improves. Increases the concentration of iron oxide inside. However, since this method is a negative factor from the viewpoint of "improving the reduction yield," it is desirable to employ the method (i) or the method (i ii) described below as much as possible.

(iii) Adjustment of the type and amount of slag material supplied as an auxiliary raw material The viscosity of varnish slag varies significantly depending on the component composition and basicity of the slag. For example, if the basicity (Cab/5in2) of the produced slag is 1 0 or less, the viscosity decreases as MgO and A120ff increase, and as the amount of chloride such as fluorite increases, the viscosity decreases. Therefore, depending on the gangue components contained in iron oxide-containing raw materials,
The viscosity is adjusted by adjusting the type and amount of slag material supplied as an auxiliary raw material and appropriately controlling the basicity and component composition of the slag.

The slag viscosity adjustment method of (i) to (i ii) above is as follows:
Since they are closely related to each other, in actual operation, a target slag viscosity is determined in advance to ensure satisfactory sludge removal performance and flow prevention effect, and the slag viscosity is adjusted continuously or intermittently. The control methods (i) to (ii) may be appropriately combined and implemented while actually measuring the slag viscosity so as to approach the target slag viscosity.

Alternatively, (chemical composition and charging amount of steelmaking raw materials), (charging method of steelmaking raw materials), (secondary combustion rate during smelting reduction operation), (composition, temperature, and temperature of hot metal sent from pig iron manufacturing equipment) ), etc., estimate the slag viscosity based on the analysis results of operational results, and adjust the amount of carbon material injected, the type of slag material, and the charging amount so that the viscosity approaches the target slag viscosity. It is also possible to control variable elements such as.

[Example] Example 1 Using a hot metal gutter type smelting reduction iron making apparatus as shown in FIG. 1, the slag viscosity was adjusted according to the flow chart shown in FIG.

That is, from the analysis results of smelting reduction iron manufacturing operations using hematite ore as the iron oxide component, (charging amount of iron ore, chemical composition, and charging method), (secondary combustion rate of smelting reduction exhaust gas), (
The reduction yield of the raw ore is calculated using the chemical composition and amount of hot metal sent from the pig iron manufacturing equipment as dependent variables, and then
(reduction yield of iron ore), and among the above analysis results, (secondary combustion rate of smelting reduction exhaust gas) and (temperature and amount of hot metal sent from pig iron manufacturing equipment) are used as dependent variables (blowout of carbonaceous material and oxygen). Furthermore, the slag composition is determined using the above (reduction yield) and (charcoal material injection amount) as dependent variables.

On the other hand, a target slag viscosity that can maintain smooth slag drainage and suppress flow is determined in advance, and the amount of auxiliary raw materials charged is adjusted so that the generated slag is equal to or less than the target slag viscosity.
The viscosity of the by-product slag is maintained at around 4 voids.

Figure 5 shows the variation in slag viscosity (A) when the above-mentioned slag viscosity adjustment method is implemented, and the variation in slag viscosity when the smelting reduction ironmaking operation is carried out under constant operating conditions without implementing this viscosity adjustment method. The slag viscosity in the former case falls within a very narrow range of 2 to 6 voids, and the variation in viscosity is small, whereas the slag viscosity in the latter case falls within a very narrow range of 2 to 6 voids. It can be seen that it fluctuates over a wide range of 13 poise.

Example 2 A smelting reduction ironmaking apparatus as shown in FIG. 1 was installed in the hot metal trough of a blast furnace with a daily production capacity of 8,000 tons, and operations were carried out to increase the production of hot metal using hematite ore as the iron oxide component. In addition, in operation,
Hot metal production increased by approximately 20% (Total Nissan hot metal production: 96,001 tons)
As such, the charging amount of hematite ore (preheating temperature 500°C) is determined to be approximately 570 kg/min, the carbon material charging amount is 965 to 87 min, and the heating oxygen injection amount is 764 Nm'/min.
The sludge discharge performance and flow rate were investigated when the viscosity of the produced slag was varied by changing the amount of quicklime injected with hematite ore as an auxiliary raw material.

The results are summarized in Table 1.

In this melt reduction process, the slag produced is Fed, Cab, etc., derived from the gangue component in the hematite ore and the quicklime charged as an auxiliary raw material.

5i02. It contains A120s, MgO, MnO, TiO, etc., but in Table 1, these slag components are divided into neutral components, acidic components, and basic components.
It is organized and shown as a ring ternary system of n0)-(S i Ox +Ti02)-(Cab).

(See Table 1 below.) As is clear from Table 1, as the amount of quicklime charged increases, the viscosity of the produced slag decreases, and the amount of slag flowing decreases accordingly. The sludge properties become better and the number of forced scrapings decreases. In particular, when the amount of limestone charged is increased until the slag viscosity is reduced to 3.0 voids, the amount of limestone is suppressed to an almost negligible level, and forced scraping of the slag becomes completely unnecessary.

[Effects of the Invention] The present invention is configured as described above, and it is possible to adjust the viscosity of slag produced as a by-product in the melting reduction process using a hot metal sluice to adjust the slag drainage performance, or to improve the flow rate during slag drainage. By suppressing this, hot metal trough type smelting reduction ironmaking can be carried out extremely smoothly and efficiently.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic vertical cross-sectional view illustrating a hot metal gutter type smelting reduction apparatus to which the present invention is adopted, and Fig. 2 shows the relationship between slag viscosity, slag discharge rate, and its fluctuation amount. Graph, Figure 3 is a graph showing the relationship between slag viscosity and flow rate, Figure 4 is a flow diagram showing an example of slag viscosity control when implementing the present invention, Figure 5 is slag when the method of the present invention is adopted. It is a graph showing the variation in viscosity in comparison with a comparative method. 1: Smelting reduction iron manufacturing equipment 2: Lid body 3: Slag culvert 4: Submerged weir 5: Overflow weir 6: Steel manufacturing raw material injection pipe 7: Oxygen injection pipe 8: Carbon material injection pipe 9: Exhaust gas duct
10: Hot metal pot; - @) Shin'heel ≧ Shin - 1; p thickness - Figure 4 Figure 5

Claims (2)

[Claims] (1) Feed ironmaking raw materials, carbonaceous materials, and oxygen to the hot metal on the hot metal gutter in pig iron manufacturing equipment to melt and reduce the iron oxide components in the ironmaking raw materials, and adjust the viscosity of slag produced as a by-product in the melting and reduction process. A hot metal trough-type smelting reduction ironmaking method characterized by adjusting the slag drainage performance. (2) Feed ironmaking raw materials, carbonaceous materials, and oxygen to the hot metal on the hot metal gutter in pig iron manufacturing equipment to melt and reduce the iron oxide components in the ironmaking raw materials, and reduce the viscosity of slag by-produced in the melting and reduction process to 10 By keeping it below poise,
A hot metal trough type smelting reduction ironmaking method characterized by suppressing flow pig iron during slag discharge.