JPH07268429A - Operating method of fluidized bed prereduction device - Google Patents

Abstract

PURPOSE:To make a reduction rate high and operation safe in a smelting reduction method of powdery ore using a smelting reduction furnace and a fluidized bed prereduction device utilizing the reducing gases discharged therefrom as fluidizing gases. CONSTITUTION:A fluidized bed prereduction device consisting of a particle circulation type fluidized bed reduction furnace 11 as a first stage and an air bubble fluidized bed reduction furnace 21 utilizing the gases discharged from this particle circulation type fluidized bed reduction furnace 11 as a second stage is formed. The pressure of the gases discharged from the particle circulation type fluidized bed reduction furnace 11 is changed by regulating the amt. of the particles stagnating in this air bubble fluidized bed reduction furnace 21, by which the velocity of flow of the gases in the fluidized bed of this particle circulation type fluidized bed reduction furnace 11 is controlled. As a result, the condition of the prereduction furnace is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smelting reduction method for powdered ores, which comprises a smelting reduction furnace and a fluidized bed preliminary reduction device that uses the reducing gas discharged from the smelting reduction furnace as a fluidizing gas. TECHNICAL FIELD The present invention relates to a method of operating a fluidized bed preliminary reduction device for granular ores. Even when the furnace conditions of the smelting reduction furnace change and the volume flow rate or temperature of the reducing gas introduced from the smelting reduction furnace into the fluidized bed preliminary reduction device changes, the gas in the fluidized bed of the reducing gas in the fluidized bed preliminary reduction device also changes. The present invention relates to a method for operating a fluidized bed preliminary reduction device that can stabilize the furnace condition of the fluidized bed preliminary reduction device by keeping the flow velocity constant.

[0002]

2. Description of the Related Art Generally, a fluidized bed reactor has a good temperature uniformity in the bed, can perform a large amount of reaction continuously, and can use fine powder without a pretreatment step such as granulation. It is considered to be applied positively as a reduction process of spheroidal ores. A device is known in which a smelting reduction furnace for powdery ores and a preliminary reduction device for powdery ores using a fluidized bed are combined. As a preliminary reduction device using such a fluidized bed, a particle circulation type fluidized bed reduction furnace as disclosed in, for example, JP-A-3-215621 is known.
As shown in FIG. 5, such a particle circulation type fluidized bed reduction apparatus has a fluidized bed preliminary reduction furnace 51, a cyclone 52 for collecting reduced iron ore powder, and a particle reservoir 5 connected to the lower portion of the cyclone.
3. A circulation path 54 for returning the reduced iron ore powder in the particle reservoir 53 to the fluidized bed preliminary reduction furnace 51. In such a particle circulation type fluidized bed reduction apparatus 50, the temperatures in the fluidized bed preliminary reduction furnace 51, the particle accumulation tank 53 and the circulation path 54 are measured, and the particle accumulation tank 53 is measured according to the temperature difference.
By controlling the supply amount of the inert gas 58 and / or the feed material 55 or the additive material 56 to be supplied into the inside, stable operation of the particle circulation type fluidized bed reduction furnace 50 is achieved.

However, in this operation, when the furnace condition of the smelting reduction furnace (not shown) changes and the volume flow rate or temperature of the reducing gas 60 introduced from the smelting reduction furnace into the fluidized bed preliminary reduction furnace 51 changes, the reduction is performed. It was difficult to keep the reduction rate of ore powder at a high value and constant. Generally, a particle circulation type fluidized bed is operated at a gas flow rate higher than the terminal velocity of particles. Therefore, in order to secure good fluidity of particles in the fluidized bed preliminary reduction furnace and prevent falling ore from the dispersion plate, it is necessary to maintain the gas flow rate in the fluidized bed preliminary reduction furnace at a certain value or higher. is there. However, if the gas flow rate becomes too high, the amount of particles jumping out of the fluidized bed preliminary reduction furnace will increase, and it will be difficult to maintain the retention amount of particles. Therefore, there is an appropriate gas flow velocity range for stable operation depending on the physical properties of the ore or reducing gas.

The range of such gas flow velocity is, for example, as disclosed in JP-A-3-183711.
It has been proposed that 2 ≦ U ₀ / U _t ≦ 20 (1) as a ratio of the superficial gas velocity U ₀ and the terminal velocity U _{t of the} ore in the fluidized bed preliminary reduction furnace.

That is, the gas flow velocity in the fluidized bed preliminary reduction furnace is, as in the above example, to keep the reduction rate of the reduced ore powder constant and to secure good fluidity of particles in the fluidized bed preliminary reduction furnace. From the standpoint of preventing falling ore from the dispersion plate, it is necessary to operate at a flow velocity within a certain appropriate range.
Since this gas flow rate is defined by the volume flow rate of the gas, the cross-sectional area of the fluidized bed preliminary reduction furnace, and the gas temperature, when the flow rate or the temperature of the reducing gas 60 used as the fluidizing gas changes, the gas flow rate also changes, and May deviate from the range.

As a method for keeping the gas flow velocity within the proper flow velocity range with respect to such a change in the flow rate of the reducing gas 60, a pressure adjusting valve or the like is installed in the exhaust gas system of the fluidized bed preliminary reduction furnace to The method of controlling the internal pressure can be easily analogized. However, since the exhaust gas from the fluidized bed preliminary reduction furnace contains a large amount of dust at a high temperature, it is difficult to control the furnace pressure with a normal pressure regulator.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique for solving the above problems. That is, in the operation of a system consisting of a smelting reduction furnace and a fluidized bed preliminary reduction furnace, using a reducing gas discharged from the smelting reduction furnace as a fluidizing gas of the fluidized bed preliminary reduction furnace, and performing a smelting reduction of powdery ores, Maintaining a constant gas velocity in the fluidized bed in the fluidized bed preliminary reduction furnace even when the volumetric flow rate or gas temperature of the reducing gas introduced into the fluidized bed preliminary reduction furnace changes due to changes in the furnace conditions of the smelting reduction furnace Stabilizes the furnace condition of the pre-reduction furnace, that is, (a) the reduction rate of the reduced ore powder can be kept constant at a high value, and (b) the good fluidity of particles in the fluidized-bed pre-reduction furnace is maintained. An object of the present invention is to provide a method for operating a fluidized bed pre-reducing device, which can be secured and can prevent falling or the like from a dispersion plate.

[0008]

As a method for solving the above problems, the present invention provides a particle circulation type fluidized bed reduction furnace and a bubbling fluidized bed using the exhaust gas of the particle circulation type fluidized bed reduction furnace as a fluidizing gas. Using a fluidized bed preliminary reduction device in combination with a reduction furnace, the amount of particles retained in the bubbling fluidized bed reduction furnace is adjusted to control the gas flow rate in the fluidized bed of the particle circulation type fluidized bed reduction furnace. This is a method of operating a fluidized bed preliminary reduction device.

In the above method, the amount of particles retained in the bubbling fluidized bed reduction furnace is adjusted according to a change in the flow rate or temperature of the gas introduced from the smelting reduction furnace into the particle circulation type fluidized bed reduction furnace, Provided is a method for operating a fluidized bed preliminary reduction device, which is characterized in that a gas flow velocity in a fluidized bed of a particle circulation type fluidized bed reduction furnace is controlled to be constant.

[0010]

As a method for solving the above problems, the inventors of the present invention use a particle circulation type fluidized bed reduction furnace as a first stage and use the exhaust gas of this particle circulation type fluidized bed reduction furnace as a fluidizing gas. We have developed a system that uses a fluidized bed preliminary reduction device with a bed reduction furnace as the second stage.

The operation of the present invention will be described with reference to FIG. FIG. 1 schematically shows the basic structure of a fluidized bed preliminary reduction device according to the present invention. The raw material ore is charged from the raw material inlet 22 of the second-stage bubbling fluidized bed reduction furnace 21, and is preheated / reduced in the bubbling fluidized bed reduction furnace 21 by the reducing gas introduced from the reducing gas introduction port 23. In this case, the flow rate of the reducing gas in the bubbling fluidized bed reduction furnace 21 is set to a range where a normal bubbling fluidized bed is formed. The preheated / reduced ore is fed by the ore transport pipe 27 to the first stage particle circulation type fluidized bed reduction furnace 1
Introduced in 1. A small amount of the reduced ore jumping out of the bubbling fluidized bed reduction furnace 21 is separated from the reducing gas by the particle collecting device 24 and supplied again into the bubbling fluidized bed reduction furnace 21 via the downcomer pipe 25.

The semi-reduced ore preheated and reduced by the bubbling fluidized bed reduction furnace 21 is supplied to the particle circulation type fluidized bed reduction furnace 11 from the raw material inlet 12. This semi-reduced ore is reduced in the particle circulation type fluidized bed reduction furnace 11 by the reducing gas introduced from the reducing gas inlet 13, discharged from the outlet 17 to the outside of the system, and charged into a melting reduction furnace not shown. . in this case,
The gas flow velocity in the fluidized bed of the reducing gas in the particle circulation type fluidized bed reduction furnace 11 is set to satisfy the above formula (1), and good fluidity of particles in the particle circulation type fluidized bed reduction furnace 11 is ensured and dispersed. Prevents falling ore from the plate. Further, the ore jumped out of the particle circulation type fluidized bed reduction furnace 11 is a particle collecting device 14
Is separated from the reducing gas by means of and is supplied again into the particle circulation type fluidized bed reducing furnace 11 via the downcomer pipe 15.

The downcomer pipe 25 in the bubbling fluidized bed reduction furnace 21.
Alternatively, in order to prevent the backflow of the reducing gas, the downflow pipe 15 in the particle circulation type fluidized bed reduction furnace 11 is disclosed in JP-A-3-215621.
It is preferable to install circulation paths 26 and 16 for returning the reduced iron ore powder in the particle reservoir tank to the fluidized bed as disclosed in Japanese Patent Laid-Open Publication No. 2003-242242. The supplied raw material ore is preheated / semi-reduced in the bubbling fluidized bed reduction furnace 21, and further, the particle circulation type fluidized bed reduction furnace 11
It is reduced to a high final reduction rate while circulating at.

At this time, the final reduction rate is (1) reducing gas flow velocity (m / s) in the fluidized bed preliminary reduction furnace 11, (2) cross-sectional area (m ² ) of the fluidized bed preliminary reduction furnace 11, (3) ) Gas inlet 1
The flow rate (Nm ³ / s) of the reducing gas (which uses the exhaust gas of the melting and reducing furnace) supplied from No. ³ , (4) the temperature (
C), and (5) the pressure inside the fluidized bed preliminary reduction furnace 11.

The fluidized bed preliminary reduction device of the present invention controls the pressure loss of gas in the bubbling fluidized bed reduction furnace 21 by adjusting the amount of ore retained in the bubbling fluidized bed reduction furnace 21.
With this effect, the pressure and the gas flow velocity in the particle circulation type fluidized bed reduction furnace 11 can be controlled.
The operation method of the fluidized bed preliminary reduction device of the present invention is to provide an ore supply rate to the bubbling fluidized bed reduction furnace or a bubbling fluidized bed reduction according to a change in the flow rate or temperature of the reducing gas introduced into the particle circulation type fluidized bed reduction furnace. The amount of ore retained in the fluidized bed preliminary reduction furnace 21 of the bubbling fluidized bed reduction furnace is changed by adjusting the ore discharge rate from the furnace, and this effect changes the pressure loss of gas in the particle circulation type fluidized bed reduction furnace 21. Then, the pressure in the particle circulation type fluidized bed reduction furnace 11 is controlled, and the gas flow velocity of the reducing gas in the particle circulation type fluidized bed reduction furnace 11 is controlled.

[0016]

EXAMPLE The results of the test operation by the apparatus of the present invention and the apparatus of the conventional example are shown in comparison. The test was conducted by changing the fluidized gas amount and investigating the amount of ore retained in the fluidized bed preliminary reduction furnace. The test conditions are shown in Table 1. The test according to the invention is shown in FIG.
It carried out using the apparatus shown in.

The particle circulation type fluidized bed reduction furnace 11 has a particle ejection port 1 from a gas dispersion plate 18 provided at a reducing gas introduction port 13.
A cylindrical shape having a height up to 9 of 1000 mm and an inner diameter of 100 mm was used. The bubbling fluidized bed reduction furnace 21 used was a cylindrical one having a height from the gas dispersion plate 28 provided in the gas inlet 23 to the particle outlet 29 of 3000 mm and an inner diameter of 150 mm.

The test according to the conventional method was carried out by using the apparatus comprising only the particle circulation type fluidized bed reduction furnace 11 shown in FIG. In the particle circulation type fluidized bed reduction furnace 11, the height from the gas dispersion plate provided in the reducing gas inlet 13 to the particle outlet 19 is 1 or less.
A cylinder having a diameter of 000 mm and an inner diameter of 100 mm was used. The test was performed while continuously supplying and discharging ore at 3.0 kg / h.

When the gas flow rate is 12 Nl / min, the amount of ore retained in the particle circulation type fluidized bed reduction furnace 11 is 3 kg and the amount of ore retained in the bubbling fluidized bed reduction furnace 21 is 1 in the present invention.
In the conventional example, the amount of residence in the particle circulation type fluidized bed reduction furnace 11 was adjusted to 3 kg, and then the gas flow rate was changed between 6 Nl / min and 18 Nl / min.

In the example of the present invention, the amount of ore retained in the bubbling fluidized bed reduction furnace 21 was changed between 3 and 60 kg with respect to the change in gas flow rate. The gas flow rate in the fluidized bed of the particle circulation type fluidized bed reduction furnace 11 and the amount of ore retained in the particle circulation type fluidized bed reduction furnace 11 when the gas flow rate was changed are shown in FIG. An example case is shown in FIG. The first and second rows in FIG. 3 are those shown in FIG.

In the case of the embodiment, a particle circulation type fluidized bed reduction furnace 1
Even if the gas flow rate supplied to No. 1 changes, it is possible to control the gas flow velocity in the particle circulation type fluidized bed reduction furnace 11 and maintain the amount of ore retained in the particle circulation type fluidized bed reduction furnace 11. It was As a result, the reduction rate of ore could be maintained at a high rate even when the gas flow rate changed.

[0022]

[Table 1]

[0023]

According to the present invention, the following effects can be obtained. (1) Even if the amount of fluidizing gas changes, the amount of ore retained in the fluidized bed preliminary reduction furnace can be maintained constant, so stable operation is possible. (2) The reduction rate of ore can be maintained at a high rate even when the fluidizing gas amount changes.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fluidized bed preliminary reduction device according to an embodiment.

FIG. 2 is a configuration diagram of a particle circulation type fluidized bed reducing apparatus used in a test.

FIG. 3 is a test chart of an example.

FIG. 4 is a test chart of a conventional example.

FIG. 5 is an explanatory view of a particle circulation type fluidized bed reduction furnace.

[Explanation of symbols]

 11 Particle Circulation Type Fluidized Bed Reduction Furnace 21 Bubbling Fluidized Bed Reduction Furnace 12, 22 Raw Material Inlet 13, 23 Reflux Gas Inlet 14, 24 Particle Collector 15, 25 Downcomer 16, 26 Circulation Path 17, 27 Outlet 18 , 28 Dispersion plate 19, 29 Ejection port

Claims (2)

[Claims] 1. A fluidized bed preliminary reduction apparatus comprising a particle circulation type fluidized bed reduction furnace and a bubbling fluidized bed reduction furnace which uses the exhaust gas of the particle circulation type fluidized bed reduction furnace as a fluidizing gas. A method of operating a fluidized bed preliminary reduction device, characterized in that the flow rate of gas in the fluidized bed of the particle circulation type fluidized bed reduction furnace is controlled by adjusting the amount of particles retained in the bubbling fluidized bed reduction furnace. 2. The particle circulation type fluidized bed, wherein the particle retention amount of the bubble fluidized bed reduction furnace is adjusted according to the change in the flow rate or temperature of the gas introduced from the melting reduction furnace into the particle circulation type fluidized bed reduction furnace. The method for operating a fluidized bed preliminary reduction device according to claim 1, wherein the gas flow velocity in the fluidized bed of the reduction furnace is controlled to be constant.