JPH0637662B2 - Fluidized bed pre-reduction method for powdered ore - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluidized bed pre-reduction method for powdered ores, and aims to stabilize the operation and productivity of the fluidized bed pre-reduction.

[Prior Art] In recent years, in ore raw materials containing iron oxide or various metal oxides, massive ores are decreasing and powdery or granular ores are increasing, and this tendency is expected to become more prominent in the future. It

In view of such a current situation, the technology of directly using powdery granular ore for smelting has been developed. For example, there is a method of directly producing molten metal from powdered ore using an apparatus relating to a fluidized bed preliminary reduction furnace and a vertical smelting reduction furnace. This method is a method of performing pre-reduction in a fluidized bed form using high temperature exhaust gas of a smelting reduction furnace as a supply source of a reducing agent and heat necessary for pre-reduction of ore containing metal oxide. According to this method, powdered ore can be directly used as a raw material without agglomerating, so that molten metal can be produced at low cost.

FIG. 2 shows a powdery granular ore pre-reduction apparatus using a fluidized bed.

The preliminary reduction furnace 1 is equipped with a powdery ore raw material supply port 4 by melting, and a supply device 6 for supplying ore from an ore hopper 7 into the furnace is installed. Further, a gas dispersion plate 3 for fluidizing the ore is provided in the lower part of the furnace. A high-temperature reducing gas supply port 8 is opened below the dispersion plate. As the reducing gas,
High temperature exhaust gas generated from a heating furnace, a reducing gas generating furnace or a smelting reducing furnace is used. This gas acts as a reducing gas and a fluidizing gas. By introducing this reducing gas into the furnace, the granular ore on the gas dispersion plate 3 is fluidized to form the fluidized bed 2 and can be fluidized and reduced. The exhaust gas from the fluidized bed 2 discharged from the preliminary reduction furnace 1 through the exhaust port 10 contains a large amount of fine ore, so it is collected and separated by the cyclone 11 and passed through the downcomer 12 and the circulation path 13 to pass through the fluidized bed. Cycle to 2. On the other hand, the preliminary reduction product is discharged from the discharge pipe 5 and transferred to a smelting reduction furnace or the like in the next step.

Japanese Patent Laid-Open No. 62-230910 discloses a fluidization method which replaces the conventional bubbling type fluidized bed, in which the gas flow velocity in the fluidized bed is set equal to or higher than the particle terminal velocity, and pre-reduced mineral powder is allowed to accompany the gas from the fluidized bed. A method has been proposed in which the discharged pre-reduction ore is collected by a cyclone, and the collected pre-reduction ore is continuously returned to the fluidized-bed pre-reduction furnace by a particle circulation device in a closed circuit while being circulated and fluidized, while being pre-reduced.

However, in the above circulating fluidized bed pre-reduction method, depending on the gas flow rate in the fluidized bed and the brand of powdered ore, collision of particles in the fluidized bed, thermal cracking of the ore itself, reduction pulverization, etc. There was a new problem that the operation became unstable and the productivity could not be secured due to the remarkable dusting of the cyclone and the deterioration of the dust collection efficiency of the cyclone and the deterioration of the fluidization state.

[Problems to be Solved by the Invention]

The present invention introduces a high-temperature reducing exhaust gas generated from a smelting reduction furnace into a fluidized bed preliminary reduction furnace that preliminarily reduces powdery ore, while in the fluidized bed preliminary reduction furnace, gas is ejected along with the gas from the fluidized bed. Equipped with a cyclone that collects pre-reduced mineral powder,
In the circulating fluidized bed preliminary reduction method, which comprises a downcomer for accumulating the collected preliminary reduced ore powder in the lower part of the cyclone and a particle circulation path for returning the prereduced ore powder in the downcomer to the fluidized bed preliminary reduction furnace, the above-mentioned problem is solved. It is intended to provide a method for suppressing the pulverization of the pre-reduced mineral powder by appropriately adjusting the gas flow velocity in the fluidized bed.

[Means for Solving the Problems]

The present invention is a fluidized bed preliminary reduction method as described above,
In the fluidized bed pre-reduction method, the gas flow velocity in the fluidized bed pre-reduction furnace is adjusted to a range defined by the content of water of crystallization of the powdered ore and the particle size of the powdered ore. is there. The range of this flow velocity can be determined by actual measurement according to each furnace.

[Action]

Many smelting reduction ironmaking methods have been proposed as a method for directly producing molten metal from powdered ore. Powdered ore is supplied to a fluidized bed pre-reduction furnace, high-temperature reducing exhaust gas discharged from the smelting reduction furnace is introduced into this fluidized bed pre-reduction furnace to pre-reduce the powdered ore, and pre-reduced powdered ore It is known as a known technique that the fuel consumption rate can be reduced by smelting and reducing smelting in a smelting reduction furnace.

In a fluidization method using a circulating fluidized bed, the gas flow velocity in the fluidized bed is higher than the terminal velocity of the particles.Therefore, depending on the range of gas flow velocity and the brand of powdered ore, collision between particles and heat of the ore in the fluidized bed may occur. Cracking and reduction powdering occur. As a result, the reduced ore powder is remarkably pulverized, which leads to a reduction in the dust collection efficiency of the cyclone and deterioration of the fluidization state, resulting in a reduction in productivity.

Therefore, the present inventors conducted various investigations in order to solve the above problems. As a result, it was found that the pulverization of the pre-reduced ore powder progressed as the content of water of crystallization in the powdered ore increased and the gas flow velocity in the fluidized bed increased. Therefore, by appropriately adjusting the fluidized bed gas flow velocity according to the average particle size of the powdered ore and the water content of crystallization of the powdered ore, it is possible to suppress the pulverization of the reduced ore powder and to operate the stable circulating pre-fluidized bed reduction furnace. Made achievable.

FIG. 1 shows this, and is a graph showing the relationship between the average particle size of powdered ores and the fluidized-bed gas flow velocity with the water content of crystallization in the powdered ores as a parameter. In the figure, CW indicates the content of crystal water in the powdery ore. An appropriate fluidized bed gas flow velocity corresponding to the average particle diameter can be determined depending on whether CW is higher or lower than 0.5%. As is clear from FIG. 1, the fluidized bed gas flow velocity can be increased as the powdery ore containing a smaller amount of crystal water is contained, and must be lowered when the contained amount of crystal water is large.

For example, if the average particle diameter of the powdered ore is x (μm) and the fluidized bed gas velocity (empty velocity) is v (m / s), then CW <0.5% 0.012x + 5.1 ≧ v ≧ 0 0.012x + 3.6> v ≧ 0.012x + 1.3 when CW> 0.5%.

〔Example〕

 As an example, an operation test was performed using the following device.

The test conditions and the results are shown in Table 1.

As shown in Table 1, in Examples 1 and 3 which were operated at an appropriate flow rate corresponding to the water content of crystallization and the particle diameter, an appropriate preliminary reduction rate could be obtained, but in the case of an inappropriate flow rate, The reduction rate became low.

〔The invention's effect〕

According to the present invention, the preliminary reduction ore production amount of 15 tons / day can be stably produced, and there is an effect that the productivity is improved by 30% or more as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the average particle size of powdered ores and the fluidized bed gas flow velocity with the content of water of crystallization in the powdered ores as a parameter, and FIG. 2 is a flow sheet of the fluidized bed preliminary reduction device. 1 ... Preliminary reduction furnace 2 ... Fluidized bed 3 ... Gas distribution plate 4 ... Raw material supply port 5 ... Discharge pipe 6 ... Supply device 7 ... Ore hopper 8 ... Gas supply port 10 ... Discharge port 11 ...... Cyclone 12 ...... Downcomer 13 ...... Circulation path

Front page continuation (72) Inventor Takashi Ushijima 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division

Claims (1)

[Claims] 1. A fluidized bed pre-reduction furnace, and a cyclone for collecting the pre-reduced mineral powder discharged from the fluidized bed along with gas.
Using a device equipped with a downcomer that stores the collected pre-reduced ore powder and a circulation path that returns the pre-reduced ore powder in the downcomer to the fluidized-bed pre-reduction furnace, when preliminarily reducing the ore in a circulating fluidized bed, A fluidized bed pre-reduction method for a powdered ore, which comprises adjusting a gas flow rate in a fluidized bed pre-reduction furnace within a range determined according to the water content of crystallization of the powdered ore and the particle size of the powdered ore.