JPH049418A - Fluidized bed prereduction furnace - Google Patents

Abstract

PURPOSE:To allow the stable prereduction of powdery ores even in a long-term operation by disposing heat resistant rods drivers which pull and insert heat resistant rods and high-frequency generators as a set to every set of the respective heat resistant rods and providing a gas diffusing device formed with the heat resistant rods in the form of a grid to the lower part of the above reduction furnace. CONSTITUTION:The gas diffusing device is formed of the grid disposed with >=1 steps of the heat resistant rods 12 made of heat resistant materials, an ultrasonic wave impressing horn 13 and an ultrasonic generator 14 as the device for impressing high-frequency oscillations to the respective heat resistant rods 12, and the driver 15 which can independently pull and insert the respective heat resistant rods 12. The above-mentioned dispersing device is installed in a gas introducing section 4 in the lower part of the fluidized bed reduction furnace 5 and the number of the heat resistant rods 12 to be inserted into the above mentioned introducing section 4 is adjusted by the above-mentioned driven 15 according to the amt. of the gases generated in the smelting reduction furnace 1 or the grain sizes of the ores to be treated. The ultrasonic oscillation of the above-mentioned generator 14 is transmitted via the above- mentioned horn 13 to the heat resistant rods 12 inserted in the introducing section 4. The sticking of the exhaust gas dusts and the ores in the sticking to the heat resistant rods 12 is prevented in this way and the stable prereduction of the powdery ores is executed even in the long-term continuous operation.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a method for producing hot metal by melting and reducing powdered iron ore using coal as a reducing agent and heat source, which utilizes exhaust gas from a smelting reduction furnace. This invention relates to a reducing gas distributor for a pre-reducing furnace for preheating and pre-reducing powdered iron ore.

<Prior art> A reduction furnace that is connected to a smelting reduction furnace to preheat and reduce powdered iron ore in the smelting reduction process is called a pre-reduction furnace. It is disclosed in JP-A No. 1-149911 and the like. It is known that connecting a preliminary reduction furnace to a smelting reduction furnace has a great effect on improving the utilization efficiency of coal, which is a heat source and a reducing agent. In such a melt reduction process, the following points are listed as conditions that the gas introduction part of the preliminary reduction furnace must meet.

■ It is possible to introduce a hot gas capable of supplying heat to maintain the reaction temperature sufficient to provide the required reduction rate.

■ Ensuring uniform and stable fluidization of powdered ore.

■ Stable flow is not inhibited by ore stinking due to localized overheating, etc.

■ Avoid causing so-called ore drop, in which the powdered ore to be fluidized falls from the reducing gas introduction section.

■ The fine dust in the exhaust gas from the smelting reduction furnace will not clog the gas disperser and worsen the gas dispersion state.

■ The performance of the gas disperser does not change even during long-term continuous operation.

In order to improve the gas utilization rate in the pre-reduction furnace, that is, to improve the ore reduction rate, it is necessary to maintain the reaction temperature in the pre-reduction furnace at a higher temperature. The temperature of the pre-reduction furnace, which is the reduction reaction layer, is maintained by the sensible heat of the introduced exhaust gas, so the temperature of the gas introduction section located downstream of the pre-reduction furnace is higher than the reaction temperature inside the pre-reduction furnace. Even if powdered ore does not stick at the temperature inside the pre-reduction furnace, it is highly likely that it will stick at the gas introduction section.

In addition, the exhaust gas generated from the smelting reduction furnace contains a large amount of sticky dust, which can clog the gas distributor at the gas introduction part to the preliminary reduction furnace, making it difficult to uniformly disperse the reducing gas. This becomes even more difficult.Furthermore, the amount of reducing gas that should be introduced into the pre-reducing furnace during tapping of the smelting reduction furnace decreases, and the amount of reducing gas fluctuates and is not constant.For these reasons, the above It is always difficult to carry out an operation that satisfies all of the following conditions.

As mentioned above, the gas disperser is one of the most important parts in a gaseous fluidized bed, and various types of gas dispersers have been devised, including flat plate type, cap type, pipe type, and fixed bed type. has been done. In addition, a fluidized bed that can be classified as a cone type in which a jet is blown into the layer from a single-hole nozzle without using a gas disperser has been developed, and a cone type fluidized bed in which the formed jet penetrates the layer surface is called a spouted bed. It is differentiated.

Preheating the fluidized bed melt reduction process, equipped with a gas disperser
When used in the preliminary reduction furnace 17, first the melt reduction furnace tJ [the gas distributor is clogged with dust contained in the gas, making continuous operation for a long time impossible. Furthermore, even if the dust in the flue gas of the smelting reduction furnace can be removed by some means, the gas disperser becomes the highest temperature in the pre-reduction furnace, and sticking occurs due to the ore, making it impossible to continue the operation. Becomes No.1. In any case, if the holes in the gas distributor become clogged, it is necessary to temporarily stop the operation and restore it.

In addition, in the pre-reduction furnace of the cone-shaped fluidized bed smelting reduction process that does not use a gas disperser, clogging does not occur due to exhaust gas dust or ore sticking, but due to fluctuations in the smelting reduction furnace exhaust gas landscape. It has the disadvantage that it cannot deal with so-called ore drop, in which powdered ore falls below the pre-reducing furnace.

Therefore, as a gas disperser that is most suitable for installation in the preliminary reduction furnace of the smelting reduction process, JP-A-59-104078 discloses a gas disperser that combines a plurality of rods made of heat-resistant material in a lattice shape. Gives internal gas dispersion effect,
A technology has been disclosed that not only ensures a uniform and stable fluidization reaction, but also eliminates the disadvantages of using a conventional gas distributor through the effect of multi-stage distribution. Although the holes are not clogged, it cannot cope with falling ore like a cone-shaped fluidized bed. In addition, if ore sticks to the lattice-like internals as a result of long-term operation, the ore flow condition in the riser will deteriorate, and it will be necessary to stop the operation and restore it.

In addition, Japanese Patent Application Laid-open No. 59-107185 discloses that a disperser is combined to produce a gas dispersion effect, and that the shape of the disperser is specified and the disperser is rotated to eliminate clogging, and that depending on the amount of reducing gas, A technique has been disclosed to deal with ore fall by adjusting the opening area. However, this method has the disadvantage that it is difficult to detect clogging between the dispersing rods, and that the flow becomes unstable when rotating the disperser to eliminate clogging.

<Problem to be solved by the invention> In response to clogging of the distribution plate, which is a major problem in the gas distributor of the pre-reduction furnace in the smelting reduction process as described above, ■ Unsteady state such as stopping ore flow in the riser. To solve this problem without causing it. Or prevent clogging of the gas distributor.

■ Even if there are fluctuations in the amount of reducing gas, there will be no occurrence of mine falls.

Accordingly, the present invention has been made in order to provide a fluidized bed pre-reduction furnace that can stably pre-reduce powdered ore even during long-term continuous operation.

<! ! Means to solve the problem〉 The inventors obtained the following findings as a result of intensive research.

As a method of satisfying both conditions (1) and (2) that the gas distributor should have above, when the diameter of the gas introduction part is constant, it is necessary that the area of the opening part is variable according to the amount of reducing gas,
Furthermore, we have come to the conclusion that not only a device for removing clogging in the gas distributor but also a clogging prevention mechanism is necessary, and based on this knowledge, we have developed the present invention.

In the present invention, a plurality of heat-resistant rods made of a heat-resistant material are arranged in one or multiple stages at the bottom of a fluidized bed pre-reduction furnace that forms a fluidized bed with high-temperature reducing gas to reduce powdered ore. A fluidized bed pre-reduction furnace characterized by being equipped with a gas distributor consisting of a grid, a high-frequency generator that applies high-frequency vibrations to each heat-resistant rod, and a drive device that can independently insert and remove each heat-resistant rod. .

<Effect> There are two types of gas distributor clogging: one is caused by exhaust gas dust and the other is caused by ore sticking. Clogging due to dust in the exhaust gas is more likely to occur as the pore size of the gas disperser becomes smaller, and the sticking phenomenon of ore is more likely to occur among fine particles with a large specific surface area, even if the particles are the same, and it also occurs from immobile particles. Even if the particles are fine, sticking will not occur if the particles are constantly moved.

Here, as a method of not producing immobile particles, it is effective to constantly apply vibrations to the particles using a heat-resistant rod to which high-frequency vibrations of the gas disperser according to the present invention are applied, and furthermore, it is effective to apply vibrations to the particles through the gas disperser. Vibration is applied to dust and stuck particles through a heat-resistant rod, so
The acceleration of vibrations also has the effect of shaking them off. In addition, it is preferable that the vibration to be applied has a small amplitude from the viewpoint of preventing gas leakage to the outside, and it has been found that one or more so-called ultrasonic vibrations are suitable for 15, which has a large acceleration. Furthermore, the application of ultrasonic vibration to the gas disperser has the effect of suppressing the generation of bubbles and, as a result, promoting the dispersion of the reducing gas.

<Example> FIG. 4 schematically shows a melt reduction process equipped with the apparatus of the present invention.

The high-temperature reducing exhaust gas generated from the melting reduction furnace 1 is transferred to a cyclone 3 for removing exhaust gas dust located in the middle of the exhaust gas duct 2.
The gas is introduced into the riser 5 from the gas introduction section 4 of the fluidized bed, which is a preliminary reduction furnace. Powdered ore led to the preliminary reduction furnace from the ore supply lower provided in the middle of the circulation path 1116 enters the riser 5 through the circulation path 6 and is reduced. The fluidized ore is separated from the reducing gas by a cyclone 8 and returned to the circulation path 6. On the other hand, the exhaust gas is sent from the exhaust gas pipe 9 to the exhaust gas treatment device 10. The pre-reduced powdered ore is also transferred to the smelting reduction furnace 1 from the ore discharge port 11 provided in the middle of the circulation path N6. If care is taken not to discharge the unreduced ore that has just been supplied to the pre-reduction furnace from the ore supply lower and ore Ut outlet 1.1, the effect will be maintained even if it is installed anywhere in the pre-reduction furnace except for the cyclone. Figure 1 shows the gas introduction section 4 of the fluidized bed pre-reduction furnace according to the present invention.
FIG.

It has a structure in which a plurality of heat-resistant l1j12 are combined in a multistage lattice shape, and an ultrasonic wave application horn 13 and an ultrasonic generator 14 are connected to each heat-resistant rod. Further, a drive device 15 for inserting and removing the heat-resistant rods 12 is also connected to each heat-resistant rod. The number of heat-resistant rods 12 inserted into the gas introduction section 4 is not constant because the projected opening cross-sectional area of the gas introduction section is adjusted depending on the amount of reducing gas generated from the smelting reduction furnace 1 and the particle size of the ore to be processed. A drive device 15 for the heat-resistant rod is required.

Ultrasonic vibrations generated by the ultrasonic generator 4 are transmitted to the heat-resistant rod 2 contained in the gas introduction part 4 via an ultrasonic applying horn 13. Therefore, it is possible to prevent ore from adhering to the heat-resistant rods 12-- due to exhaust gas dust and sticking. When this heat-resistant rod 12 is inserted into the gas introduction part 4, ultrasonic waves are always applied to it, so the gas dispersion state is always the same and an unsteady state is not good.6 Heat-resistant rod 12 and ultrasonic waves Sound wave applying hoe 713 and ultrasonic generator 1
A heat-resistant rod drive device 15 is provided for each set of heat-resistant rods, which can insert and remove the entire set of heat-resistant rods.

Example 1 A hematite ore produced in South America having a particle size composition as shown in Table 1 was reduced in a melting and reduction equipment as shown in FIG. 4 equipped with a gas disperser according to the present invention as shown in FIG. 1. Explain. Here, the processing conditions including the ultrasonic application conditions are shown in Table 2.

As a comparative example, reduction treatment was performed using the same apparatus and the same ore as in the example without applying ultrasonic vibration to the heat-resistant rod 12, and the clogging state of the gas disperser and the ore reduction rate were compared.

Table 3 shows the results of the reduction treatment.

Figure 2 shows the relationship between the additional frequency and clogging of the gas distributor.
Figure 3 shows the relationship between the additional frequency and the ore reduction rate.When high-frequency vibrations are applied to the zero disperser, the clogging of the disperser is slighter than when high-frequency vibrations are not applied, especially when the frequency is 1.
No clogging was observed in the case of 5kllz to 20kl)z. Although there is no significant difference in the stone reduction rate between the two, when the frequency of the added vibration is 10 kllz or more, the reduction rate improves by about 5% compared to when high frequency vibration is not applied.

As described above, the effects of the present invention were clearly recognized in terms of both clogging of the gas disperser and improvement of the ore reduction rate.

Table 3 <Effects of the Invention> According to the fluidized bed pre-reduction furnace according to the present invention, clogging of the gas disperser was significantly reduced, stable pre-reduction of granular ore could be performed for a long period of time, and the reduction rate was also improved.

[Brief explanation of drawings]

Fig. 1 is a detailed view of the gas introduction part according to the present invention, (a) is a side sectional view, (b) is a sectional view taken along the line X-X in (a), and Fig. 2 shows clogging and addition of the gas distributor. FIG. 3 is a characteristic diagram showing the relationship between the frequency of vibration and FIG. 3 is a characteristic diagram showing the relationship between the ore reduction rate and the frequency of additional vibration. FIG. 4 is a schematic diagram of the smelting reduction process equipped with the apparatus of the present invention. It is. 1... Melting reduction furnace, 2... Wandering gas duct, 3
...Cyclone for exhaust gas dust removal, 4...Gas introduction part, 5...Preliminary reduction furnace, 6...Circulation path,
7... Ore supply port, 8... Cyclone for ore collection, 9... Exhaust gas pipe, IO... Exhaust gas treatment device,
11... Ore discharge port, 12... Heat-resistant rod, 13.
...Ultrasonic application horn, 14... Ultrasonic generator, 15... Heat-resistant rod drive device, 16... Fluidized bed, 17... Reducing gas.

Claims (1)

[Claims] At the bottom of the fluidized bed pre-reduction furnace, which forms a fluidized bed with high-temperature reducing gas to reduce powdered ore, there is a grid in which a plurality of heat-resistant rods made of heat-resistant material are arranged in one or multiple stages, and each A fluidized bed pre-reducing furnace characterized by being equipped with a gas distributor comprising a high-frequency generator that applies high-frequency vibrations to heat-resistant rods, and a drive device that can independently insert and remove each heat-resistant rod.