JPH01195224A - Operating method for molten iron gutter type smelting reduction iron manufacture - Google Patents

Abstract

PURPOSE:To reduce iron manufacturing cost by recovering CO-contg. gas produced from a smelting reduction iron manufacturing device and utilizing it for fuel or reduction. CONSTITUTION:An iron manufacturing raw material, carbon material and oxygen are fed to the molten iron flowing through a molten iron gutter and the iron oxide component incorporated in the above-mentioned raw material is melted and reduced. CO-contg. gas produced from this process is recovered and it is utilized as valuable gas for fuel or reduction after removing dust.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses hot metal flowing out from a pig iron production device through a hot metal trough as a heat source, and utilizes carbon in the hot metal as a reducing agent. Regarding the improvement of a method for producing iron by melting and reducing iron ore, pre-reduced iron ore, scrap, and other raw materials for steelmaking by supplementing carbonaceous material and oxygen, it is particularly important to reduce the amount of CO-containing gas produced in the melting and reduction process. The present invention relates to a method that can improve the economic efficiency of factory operations by effectively utilizing the gas as a gas.

[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 rapid smelting reduction method.Currently, the blast furnace method, which allows continuous operation and is suitable for mass production, is the mainstream. It becomes.

However, in addition to the problem of requiring enormous construction and maintenance costs, the blast furnace method uses a vertical moving bed reaction, so in order to improve operational efficiency and stability, it is necessary to use a method that acts as a reducing agent. 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. Typical methods include methods using a rotary furnace, methods using a converter type iron bath furnace, and coke-filled methods. 3f of method using vertical furnace! However, a 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 the tapping and slag are produced in 1 to 2 batches, for example.
Since the operations are carried out intermittently over time, compared to the continuous method using a blast furnace, not only are the tapping and slag tapping operations and their post-processing operations cumbersome, but the post-processing furnace is cooled each time, resulting in lower thermal efficiency. Moreover, in order to increase productivity, a certain amount of hot metal and molten slag must be stored in the furnace, so a fairly 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 pig iron manufacturing equipment such as blast furnaces, cupolas, or smelting reduction iron making equipment (hereinafter simply referred to as pig iron manufacturing equipment), and the We have developed a method for melting and reducing raw materials for steelmaking using carbon as a reducing agent, and have already filed a patent application (
(Japanese Patent Application No. 186400/1982, 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, and utilizes the carbon contained in the hot metal as the main reducing agent, further eliminating the shortage of heat sources and reducing agents. This method involves injecting ironmaking raw materials into hot metal to perform smelting reduction while supplying carbonaceous materials and combustion oxygen to supplement the process. ■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.

By the way, the above-mentioned melt reduction reaction is carried out under a reducing atmosphere, and specifically, a reducing gas mainly composed of co produced by combustion of carbonaceous material is used. Although this reducing gas contributes to the reduction reaction and the degree of reduction is slightly reduced, it still has considerable reducing properties, but the prior invention does not discuss how to use this reducing gas more effectively. No special consideration was given.

The present invention has been made in view of the above-mentioned situation, and its purpose is to make it possible to further utilize a large amount of reducing gas, which is produced as a by-product in the molten iron trough type smelting reduction iron manufacturing process, as a valuable gas. The aim is to reduce the operating costs of the entire steel mill.

[Means for Solving the Problems] The structure of the iron manufacturing operation method according to the present invention that can solve the above problems is that the hot metal flowing through the hot metal gutter of the pig iron manufacturing equipment,
The purpose is to supply ironmaking raw materials, carbonaceous materials, and oxygen, and melt and reduce the iron oxide components in the ironmaking raw materials, and the CO-containing gas recovered here is used as a valuable gas after dust removal. be.

[Function] A feature of the present invention is that reducing gas produced mainly by combustion of carbonaceous material is effectively utilized as a valuable gas when performing smelting reduction ironmaking on a hot metal sluice provided in a pig iron manufacturing apparatus as described above. do.

For example, FIG. 1 is a schematic vertical cross-sectional explanatory diagram illustrating a smelting reduction iron manufacturing facility to which the present invention is applied, and FIG. 2 is a schematic flow diagram illustrating an embodiment of the operating method of the present invention including an exhaust gas utilization system.

First, in Fig. 1, 1 is a smelting reduction ironmaking equipment installed in the middle of a hot metal trough, 2 is a lid that covers the upper part of the equipment 1 and prevents the dissipation of heat and exhaust gas, 3 is a slag trough, 4 5 is a submerged weir, 5 is an overflow base, 6 is a steelmaking raw material blowing pipe, 7 is an oxygen blowing pipe, 8 is a carbon material blowing pipe, 9 is an exhaust gas duct, 10 is a hot metal pot, M is hot metal, S is molten iron. Slag and C indicate carbonaceous material, respectively.

Of the hot metal and molten slag that are discharged from the pig iron manufacturing equipment such as the blast furnace (numeral 11 in Figure 2) through the hot metal gutter, the molten slag with a lower specific gravity is separated at a suitable location on the upstream side up to the smelting reduction steelmaking equipment 1 shown in the figure. removed.

Then, a slightly deeper retention section is provided in the molten metal trough at a suitable location downstream, thereby forming the smelting reduction iron making equipment 1 as shown in the figure. That is, this smelting reduction iron manufacturing equipment 1 includes a lid body 2 that serves both to prevent heat radiation and exhaust gas diffusion, a steel manufacturing raw material blowing pipe 6, and an oxygen blowing pipe 7.
, a carbonaceous material blowing pipe 8 and an exhaust gas duct 9 are installed, and from the steelmaking raw material blowing pipe 6, iron-containing raw materials such as iron ore, pre-reduced ore, scrap, etc. and auxiliary raw materials such as quicklime are injected into hot metal in an appropriate ratio. At the same time, powdery carbonaceous material C is blown in from the carbonaceous material blowing pipe 8, and at the same time, oxygen (or air) is blown in from the oxygen blowing pipe 7. The iron making 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 carbonaceous material, and the iron oxide component in the iron making raw material is mixed with the iron oxide contained in a large amount in the hot metal M and the blown coal. Material C and the carbon material C
is reduced by the action of carbon monoxide produced by combustion. The generated iron is then taken into the hot metal M.
On the other hand, the slag component S having a small specific gravity flows down one after another while floating on the surface of the hot metal M, and is separated and discharged from the slag drain 3.

Although Fig. 1 shows an example in which raw materials for steelmaking, carbonaceous material, and oxygen (air) are blown in separately, these three may be blown in in a mixed state from one blowing pipe, or they can be blown in at any time. It is also possible to properly mix and inject a combination of these, and furthermore, it is also possible to inject ironmaking raw materials, carbonaceous materials, etc. from multiple locations along the flow direction of the hot metal flow, and to proceed with the reduction reaction at multiple locations. Although it is most effective to blow the carbonaceous material C into the hot metal, in some cases it can also be dispersed above the hot metal flow and mixed into the hot metal by the ripples on the hot metal surface.

By the way, in the above-mentioned smelting reduction steelmaking process, 50% of CO is
A large amount of reducing gas containing ~90% is produced,
In the present invention, this CO-containing gas is sucked through the exhaust gas duct 9 and can be effectively used as a valuable gas according to the flow shown in FIG. 2, for example.

That is, the high-temperature CO-containing gas extracted from the exhaust gas duct 9 of the smelting reduction steelmaking equipment 1 is passed through the heat exchanger 12 to be used for preheating the steelmaking raw material, and then cooled by the cooler 13 and then passed through the venturi scrubber 14 or By passing through dust removal equipment that combines a cyclone 15 and an electrostatic precipitator 16, dust made of pulverized coal, pulverized ore, etc. is removed, and the gas is converted into clean gas with combustibility and reducing properties, such as the steel manufacturing equipment or its related equipment. It is used as valuable gas. In the illustrated example, the dust-removed co-containing gas is passed through the booster blower 17 to increase the pressure and further increase the reduction energy. [III] Reducing gas blown in from the blast furnace tuyere, [rVl] It can be used as a fuel gas for a hot blast furnace for blast furnaces, etc. In other words, the co-containing gas recovered in the present invention can be effectively used for various purposes as a fuel gas or reducing gas, but as shown in Fig. If used effectively, it can contribute to reducing the running cost of the equipment as a whole, which in turn can be reflected in a reduction in ironmaking costs. To the same effect, when pre-reduced ore is used as a raw material for iron ore, it is also effective to use the CO-containing gas for pre-reduction of iron ore. In addition, in blast furnace equipment, a large amount of CO-containing gas is discharged from the top of the furnace, but this gas is also useful as a reducing gas or fuel, and also contains a large amount of dust, so it is necessary to perform cooling, dust removal, and pressurization functions. It is customary to collect exhaust gas in an exhaust gas treatment facility 19 equipped with a. Therefore, as shown in Fig. 2, for example, if the smelting reduction exhaust gas is combined with the blast furnace exhaust gas line and sent to the exhaust gas treatment equipment 19, where it is cooled, dust removed, pressurized, etc. together with the blast furnace exhaust gas, it is possible to This is preferable because exhaust gas treatment equipment can be omitted and equipment costs and operating costs can be reduced.

[Example] In the hot metal gutter of a blast furnace facility with a production capacity of 8,000 tons, the first
A smelting reduction iron manufacturing equipment as shown in the figure is installed, and hematite ore or scrap is used as the iron oxide component.
Smelting reduction iron production was carried out under the conditions shown in the table, and approximately 1400)
The company carried out increased hot metal production operations at a rate of 17.5% per day (17.5% increase in production rate).

Table 1 As a result, in all cases, steady operation was achieved within a two-day preparation period, including adjustment of hot metal temperature, smooth treatment of tailings (adjustment of auxiliary raw materials, etc.), and stabilization of exhaust gas recovery equipment. It was confirmed that it reached.

On the other hand, by changing the blast furnace operating conditions, the amount of iron production can be increased by 8.
Production from 8,000 tons to 9,400 tons (increase in production by 1,400 tons)
In order to increase production by approximately 2% per day), it is necessary to increase the amount of air blown into the blast furnace by approximately 20%, and past results indicate that the furnace operating condition must be stabilized every time the amount of air blown is increased by approximately 2%. The amount of air blown must be increased in stages (usually taking about 1 week to 10 days), and the above-mentioned increased production volume of 1400
It is thought that it will take about 3 months to achieve this rate per ton/day, and this trend is the same when reducing the amount of iron production.

That is, according to the hot metal gutter type smelting reduction ironmaking operation method of the present invention, compared to the method of changing the blast furnace operating conditions, it is possible to increase or decrease the production of pig iron in a much shorter preparation period, and it is possible to increase or decrease the production of pig iron in accordance with the target pig iron production amount. This makes it possible to flexibly adapt production plans.

In addition, when implementing the production increase method shown in Table 1 above, CO-containing gas discharged from smelting reduction steelmaking equipment is replaced with a portion of LPG or heavy oil as fuel for the existing power generation boiler in the steelmaking factory. The pig iron making cost was determined by taking into consideration the reduction in fuel cost that accompanies the effective utilization of iron, and the pig iron making cost index was calculated when the pig iron making cost in the normal blast furnace pig iron making method is set to 1.

The results are as shown in Figure 3. When scrap was used as a raw material for steelmaking, the unit price of scrap itself was high and the amount of CO-containing gas produced was relatively small, so the ironmaking cost was rather high. It can be seen that when ore is used, pig iron production can be increased at about 80% of the cost when using the normal blast furnace method.

[Effects of the Invention] The present invention is configured as described above, and it is easy to increase or decrease production of pig iron, and the degree of freedom in hot metal production planning is high.Moreover, CO-containing gas by-produced in smelting reduction ironmaking equipment is used as a fuel gas. Alternatively, by effectively using it as a reducing gas, it has become possible to reduce ironmaking costs.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical cross-sectional view illustrating hot metal trough type smelting reduction ironmaking equipment, Fig. 2 is a schematic flow diagram showing an embodiment of the present invention, and Fig. 3 is a schematic longitudinal sectional view illustrating a hot metal gutter type smelting reduction iron manufacturing equipment. It is a graph showing a comparison of pig iron cost indexes. 1... Smelting reduction iron manufacturing equipment 2... Lid body 3... Slag gutter 4... Submerged weir 5... Overflow weir 6... Steel manufacturing raw material blowing pipe 7... Oxygen injection Pipe 8... Carbon material injection pipe 9...
・Exhaust gas duct 10...Hot metal pot 11...Blast furnace
12... Heat exchanger 13... Cooler 14... Venturi scrubber 15... Cyclone separator 16... Electrostatic precipitator 17... Boosting blower 1
8... Heating furnace 19... Exhaust gas treatment equipment Figure 3

Claims (1)

[Claims] (1) Iron-making raw materials, carbonaceous materials, and oxygen are supplied to the hot metal flowing through the hot-metal gutter of a pig iron production equipment, and the iron oxide component in the iron-making raw materials is melted and reduced, and the CO-containing gas recovered here is removed from dust. A hot metal trough type smelting reduction ironmaking operation method characterized by using the hot metal as post-valuable gas.