JPS61201739A - Treating method of sintered ore - Google Patents

Abstract

PURPOSE:To manufacture sintered ore superior in reduction powdering property and reducibility, by detecting a wind box attaining to a prescribed temp. by waste gas thermometer provided at wind box group of sintering machine, and sucking and introducing reducing gas against the subsequent wind box group. CONSTITUTION:In Dwight-Lloyd sintering manufacture of self-fluxing sintered ore in which surface of an blended material 2 charged on a running pallet 1 of sintering machine is fired by a firing furnace 3, air is sucked and introduced through the material 2 by the wind box arranged under sintering machine strand to form a sintering high temp. zone 4 and to obtain a sintered ore layer 9, at a specified wind box position 6 as the boundary where waste gas thermometer (figure is omitted) arranged at the box 5 group, reducing gas supplied from a reducing gas holder 14 is sucked and introduced through a hood 13 against the following latter half boxes 5. In this way, sintered ore is prereduced lightly, to decrease reduction powdering phenomenon and improve reducibility thereof in blast furnace and the operation is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for treating sintered ore, and more specifically,
The present invention relates to a method for treating sintered ore that can reduce the reduction and powdering phenomenon in a blast furnace, thereby stabilizing blast furnace operation.

(Prior technology) Currently, most sintered ore for iron manufacturing is produced using continuous Dwight Lloyd type sintering machines. An appropriate amount of coke powder is mixed, water is added to the mixture, and the mixture is granulated using a drum mixer, etc., and then loaded onto the pallet of the sintering machine. It mainly consists of a group of box-shaped pallets that move with each other, a plurality of partitions fixed to the bottom of the pallets, and a group of wind boxes that are connected to a suction and exhaust fan via ducts. Charged onto the grate at the bottom of the pallet: R+, fc iron ore mixed raw materials are ignited in the ignition furnace by the coke powder on the surface layer (C burner). The sintering reaction continues sequentially from the upper layer to the lower layer.In the latter half of the sintering machine, the sintering reaction zone (maximum temperature 1300°C to 1350'C) that has descended in the sintering layer as described above is exposed to the pallet grate. After reaching the surface, the sintered layer, which has no fuel, is cooled by ventilation and then discharged to the next crushing process.

The sintered ore produced in this way is transported on a belt conveyor after undergoing a sintering process and then used in a blast furnace, but one of the problems with the properties of current sintered ore is The first is the reduction and pulverization phenomenon of sintered ore that occurs in the low-temperature reduction zone at the top of the shaft in the blast furnace.

It is well known that this phenomenon is mainly unique to the basic sintered ore blended with limestone as a solvent.
It is a fact that the specific shape of hematite (Feze3) present in sintered ore is found in the low temperature range (
500℃~600℃) (FesO4
) The accepted explanation is that the internal strain that occurs as the crystal lattice expands during the transformation of the sintered ore during the reduction reaction triggers the generation and propagation of cracks in the sintered ore structure, leading to pulverization.
Many reports related to the powdering phenomenon have been submitted. If this phenomenon of reduction and pulverization of sintered ore becomes excessive, it obstructs the permeability of the charge packed bed in the blast furnace, increases pressure loss, and increases the frequency of so-called shelving and slipping during blast furnace operation. We are well aware that this can lead to instability.

Therefore, in order to prevent the sintered ore from being excessively reduced and powdered in the blast furnace, the sintered ore manufacturing side conducted a simplified reduction powdering test (R
Daily quality control is carried out using DI index).

In addition, in terms of sinter production technology, various quality improvement techniques have been attempted to maintain a good RDI index of sinter, but the above-mentioned specific shape of hematite is the basic measure to prevent reduction and powdering. The main policy is to suppress generation.

Here, if we infer the mineral formation process of sintered ore based on conventional knowledge, we can think of the following: First, the raw material iron ore for sintering is hematite (Hematite) F
Eze3 is the main component, and this is called primary hematite in the sense before the sintering reaction.The sintering reaction is usually performed by adding iron ore to limestone as a solvent, and coke powder as a fuel. This was carried out using a mixture containing 5% by weight, but during the rapid heating and cooling process to around 1300°C for several minutes, the reaction and melting of the CaO component in the limestone and the Feze3 component in the iron ore proceeded, and in this process, , a calcium ferrite-based melt and a silicate slag-based melt are generated, and during the cooling process, these melts solidify and bond unmolten ore and pores to form sintered ore. The iron oxide components melted during this high-temperature melting process become supersaturated during the cooling and solidification process, and some of them crystallize and grow from the melt and appear as crystals in the sintered ore structure. This is secondary hematite and secondary magnetite.
In particular, secondary hematite, which has grown coarsely during this process, is said to be the main cause of deterioration in reduction and pulverization of sintered ore.

Therefore, the prior art is mainly composed of techniques intended to suppress the production of hematite in a specific shape, which is the main cause of reduction and pulverization at the time of producing sintered ore. One method is to reduce hematite to magnetite during the sintering reaction process by, for example, increasing the proportion of coke powder in the raw materials to increase the calcination temperature and strengthen the reducing atmosphere. I'm here.

On the other hand, for example, in JP-A-52-107213 and JP-A-55-69227, sintered ore produced by a conventional method is charged into a blast furnace in a separately equipped shaft furnace before being charged into a blast furnace. A method has been proposed in which the sintered ore, especially the slag part, is modified by carrying out a countercurrent contact treatment with the furnace top gas, for example, to improve the room temperature strength and reduction powder strength.0 (Problems to be Solved by the Invention) However, the method of reducing hematite to magnetite in the sintering reaction process by increasing the calcination temperature and strengthening the reducing atmosphere by increasing the blending ratio of coke powder in the blended raw materials is expected to improve RDI, but There are many cases in which reducing properties, which are important properties for charging materials, are deteriorated. That is, an increase in the blending ratio of coke powder increases the amount of melt and reduces the porosity in the sintered ore, and an increase in the amount of magnetite means that minerals with poor reducibility are themselves surrounded by slag during production. This is to become.

In this way, when considering the quality (strength and reducibility) other than reduction and powdering comprehensively, there is still no technology that completely prevents the crystallization of coarse secondary hematite with the above specific shape. Currently, it is not fully established.

Mayu, there is a method for reforming sintered ore, especially the slag part, by bringing it into countercurrent contact with blast furnace top gas in a shaft furnace.
In addition to the conventional process, it is necessary to install a shaft furnace, which is undesirable because it requires a large amount of construction cost. Furthermore, the practical effects are not necessarily clear.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a method for injecting a reducing gas into the sintered ore lump immediately after the sintering reaction is completed in the latter half of the sintered ore production. By introducing suction and performing a mild preliminary reduction treatment, a embrittlement area due to hematite → magnetite reduction is artificially generated inside the sintered ore lump, which reduces the burden of subsequent processes such as crushing and sizing of the sintered ore. At the same time, it also reduces the reduction powdering phenomenon inside the blast furnace, contributing to the stabilization of blast furnace operation.
In particular, the idea and method are completely different from the former method, and it does not suppress the production of hematite with a specific shape, which is considered to be the main cause of reduction powdering, but forces the production of hematite. The purpose of the present invention is to provide a method that substantially eliminates the generation of powder caused by the reduction and pulverization of sintered ore in a blast furnace by producing sintered ore that has been specially treated.

Before explaining the present invention in more detail, the conventional sintering method will first be explained. Fig. 4 is a schematic diagram of the conventional sintering method. 2 is operated in such a way that the surface layer is ignited in the ignition furnace 3 and the sintering reaction of the entire layer down to the lower layer is completed in the process of reaching the ore discharge end of the sintering machine. Sintering raw material ore and solvent limestone cause a melting reaction by burning fuel powder coke 120
The high temperature zone 4 above 0°C has already reached the lowest sintering layer at a position upstream from the sintering machine discharge end (as a guide, 80 to 85 m of the sintering machine length), and this is due to the individual wind This is recognized because the exhaust gas thermometer installed in box 5 shows a temperature increase from this position to the ore discharge side.From this specific position 6 (hereinafter referred to as frame front point F, F, P) onwards The main focus of this process is to maintain a high temperature in terms of heat balance and then to cool the sintered ore lump (sintered cake). The role of coke combustion air is replaced by that of a ninth medium of heat exchange and cooling.

Therefore, the latter half of the sintering machine after F, F, P does not need to be air containing oxygen, and may be any other type of gas as long as it is a fluid that plays the role of upper air.

In addition, in FIG. 4, 7 is a mixed raw material hopper, 8 is a wet raw material layer, 9 is a sintered ore layer, 10 is a main exhaust pipe, 11 is a dust collector,
12 is a main exhaust fan.

On the other hand, looking at the quality of the sintered ore lump fired on a sintering machine, the sintering process is a process in which sequential chemical reactions and heat transfer proceed from the upper layer to the lower layer, so the lower layer has more The melting of the raw material ores progresses further, and the crystals in the sintered ore structure also grow. The quality of the sintered ore obtained as a result of this generally has deviations in the vertical direction of the sintered layer, and although the porosity of the lower layer decreases and the strength improves due to the improvement in the degree of melting, the coarseness of the secondary hematite increases. As a result of the progress of crystallization, reduction and powdering properties deteriorate.

In view of the above points, the inventors of the present invention have focused on reducing and powdering the lower sintered layer, which is characteristic of the current sintering process, by changing the gas type in the latter half of the sintering machine. The present invention has been made based on the knowledge that the improvement is expected to be n. That is, the present invention has a specific position 6 where the high temperature zone 4 of the sintered layer reaches the lowest layer, and On the side,
A specific position 6 where the high temperature zone 4 of the zero sintered layer reaches the lowest layer is a wind box, which is characterized by blowing reducing gas from the upper layer of the sintered ore and subjecting the sintered ore to a slight preliminary reduction treatment. At positions F, F, and P, where the exhaust gas temperature begins to rise, an exhaust gas thermometer (not shown) installed in the wind box group 5 at the bottom of the sintering machine strand indicates a predetermined temperature, for example, about 100°C. You can know by reaching .

A method of injecting reducing gas into the sintered ore is, for example, as shown in FIG. It is introduced into the sintered ore layer by the suction force of the wind box 5.

The reducing gas injected in this way reacts with the surface of the sintered ore lump in the lower layer, which still has a temperature of 800°C or higher, reducing the hematite in the sintered ore structure that came into contact with the gas to magnetite. , the reducing components in the gas are oxidized (
For example, if blast furnace gas or converter gas containing CO as a reducing component is used, it will change to CO2)0 Also, a small amount of heat is generated at the same time as the reduction reaction, but this is generated as sensible heat of the sintered ore or gas. The recovered gas does not interfere in any way with the progress of the reaction, and the introduced gas not only carries out the above-mentioned chemical reaction, but also plays a role in cooling the sintered ore lump. The amount of reducing gas injected should be adjusted depending on the production rate of the sintered ore and the size of the high temperature zone in the lower layer of the sintered layer.This can be easily done by analyzing the exhaust gas in the final windbox using a well-known method. It is possible to detect

Note that sintering air is sucked and introduced to the wind box groups on the front half side, that is, upstream side of the above-mentioned specific position 6, as in the past. 10,
Figure 2 shows a sintering machine used to recover the sensible heat of the exhaust gas heat-exchanged in the sintering reaction and some additional sensible heat of the exhaust gas generated by the gas reduction reaction. After the exhaust gas from the lower half wind box 5 is removed from dust 15, the exhaust gas is passed through the heat exchanger 16 and then merged into the main exhaust system 10 again. This does not impair the basic structure of the present invention in any way. Considering the pressure loss of the dust remover 15 and the heat exchanger 16, it is natural to incorporate an auxiliary blower 17 into the heat recovery system.

(Function) According to the present invention, the coarse secondary hematite (especially Coarse secondary hematite is easily formed on the surface of sintered ore that is in contact with the pores and has a highly oxidizing atmosphere.] It is converted into magnetite during the entire sintered ore manufacturing process, and is forcibly converted to magnetite before being charged into the blast furnace. This causes reduction powdering.The sintered ore that has been sized and refined through this treatment has almost no causes of reduction powdering in the blast furnace, so blast furnace operations can be maintained at a high level of stability. In addition, the magnetite produced by gas reduction from the secondary hematite in the NFC sintered ore subjected to this treatment undergoes an initial reduction reaction in the low-temperature section of the blast furnace before being charged into the blast furnace. As a result, the reducibility is good and one step ahead, and fuel consumption during blast furnace operation can be reduced.Ancillary effects include the reduction in sintering in the upper and lower layers of the sintering machine. In order to artificially cause a reduction and pulverization effect on the concretion lump, the sintered ore that is discharged from the sintering machine pallet is easily crushed, reducing the power consumption of the crusher, and then sintering is performed. There is a possibility that over-grinding of ore can be prevented.0 (Example) The effects of implementing the method of the present invention will be shown in comparison with the conventional method.

Table 1 shows the ore properties and formulation table of the sintering pot test conducted to confirm the basic effects of the method of the present invention. As for the raw materials for Izn, we used those that are not generally used in the actual sintered ore production process. Figure 3 shows an experimental device in which a sintering test was conducted using the raw materials listed in Table 1. showed that. In the figure, 18 is an ore thermometer, 19 is a windbox thermometer, 20 is a dust collector, 21 is an orifice, and 22 is a proa. The specifications of this experimental device are shown in Table 2.

The raw materials listed in Table 1 were thoroughly mixed by rolling in a drum mixer for 3 minutes, then water was added so that the average moisture content was 5.5% by weight (wet basis), and the mixer was continued for an additional 3 minutes. The resulting granulated raw materials were charged into a sintered test steel and the surface layer was ignited for 1 minute with a gas burner, and then granulated by air suction from an exhaust fan. A friend that allows the sintering reaction to proceed. Therefore, in the latter stage when the sintering reaction progresses from the upper layer to the lower layer, a hood is placed on the top of the test pot from the point when the gas temperature starts to rise to 100°C, which is placed in the wind box below the raw material layer. From this, 3.0 m7 of reducing gas (blast furnace gas was used in this example) was set.
This state was maintained until the sintering reaction was completed by blowing at a constant rate.

Table 3 shows a comparison of the sintering test results obtained by the method of the present invention in which reducing gas was blown in the latter half of sintering and the conventional method in which no gas was blown. In Examples 1 to 3, the timing to start blowing the reducing gas was set to 1 when the exhaust gas temperature reached 100°C.
In order to examine the influence of fluctuations in F, F, and P that are actually expected,
According to the results in Table 2, the yield tended to decrease slightly due to the artificially generated reduction powdering effect, but the reason why the yield did not deteriorate significantly was due to the reduction of reducing gas. This is thought to be due to the fact that the powder ratio after crushing remained slight due to the flow through the pores of the sintered ore lump. The effect was extremely large, and no significant improvement was observed. Even if the slight decrease in yield is subtracted from this result, it seems that the effect contributing to stabilization of blast furnace operation is significant.

Although blast furnace gas was used as the reducing gas in this embodiment, the present invention is not limited to blast furnace gas in view of the basic principle of the present invention. However, it is important to ensure the safety of gas handling during the blowing operation, and that it is not desirable for unreacted reducing gas to escape into the sintering exhaust system after the reduction reaction. A gas with a weakly reducing composition that can reduce the lumps under low pressure is sufficient to achieve the purpose, and it is also important to take into consideration that there will be a surplus of blast furnace gas in the future.
For example, it is considered that the blast furnace gas used in this example is the most appropriate. While using standard equipment, it is possible to produce sintered ore that has significantly improved reductive powdering properties and excellent reducibility compared to conventional methods.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing an overview of the method of the present invention, Figure 3 is an explanatory diagram showing the equipment used for the sintered steel test, and Figure 4 is a diagram showing the conventional sintered ore manufacturing method. . 1. Pallet 2. Mixed material 3. Ignition furnace 4
・・Sintered layer high temperature zone 5・・Wind box 6・・F, F, P
lo・・Main exhaust pipe 13・・Hood 14・・Reducing gas holder 15・・Dust collector 16・
・Heat exchanger 17...Proa Figure 1 Figure 2 Figure 3 Procedural amendment (voluntary) Patent application filed on March 5, 1985 March 4, 1985 (1) 2 shots "0 name Sintering Processing method for mulch 3. Relationship with the case of the person making the amendment. Patent applicant 4. Agent. Table 1 (Properties and composition of raw material ores used in the sintering pot test) Part 2
Table (experimental equipment specifications)

Claims (1)

[Claims] (1) In the Dwight Lloyd type sinter production method for self-fusing sintered ore, the exhaust gas thermometer installed in the wind box group at the bottom of the sintering machine strand reaches a predetermined temperature. A method for processing sintered ore, characterized in that the sintered ore is subjected to a slight preliminary reduction treatment by sucking and introducing reducing gas into the wind box group on the latter half side.