JPH0715129B2 - Method for producing molten metal from powdered ore - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing molten metal from powdered ore containing a metal oxide, and more specifically, a fluidized bed is formed in the upper stage and carbon is formed in the lower stage. The present invention relates to an operating method by controlling the depth (called jet depth) of a raceway space created by gas blown into a packed bed of a vertical smelting reduction furnace in which a packed bed of a solid reducing agent is formed.

[Conventional technology]

Iron ore and other metal ore resources are made up of powdered ores, and the ratio of powdered ores tends to increase in the future. Especially, in order to improve the quality of low-grade powdered ore, flotation, magnetic separation, etc. are performed, and it is expected that the ratio of fine ore will increase. The method of agglomerating powdered ore and then reducing it to obtain molten metal requires the cost for agglomeration, so agglomeration is omitted and powdered ore is directly melted using a fluidized bed. Methods and devices for reduction have been developed.

Japanese Patent Publication No. 60-45682 discloses a technique for smelting and reducing powdery ore using a fluidized bed, which includes a second fluidized bed region and a blowing nozzle which are substantially formed by coke particles having a particle size of 10 to 30 mm. Although there is a description of the mounting position, angle, etc., the jet depth of the blown gas is not explained.

[Problems to be solved by the invention]

In such a vertical reduction furnace, a packed bed of carbon-based solid reducing agent and a fluidized bed above it are charged from the top of the furnace with the carbon-based solid reducing agent, and powdered ore together with oxygen is added to the carbon-based solid reducing agent. In a fluidized bed, and the gas containing oxygen is blown into the packed bed of the carbon-based solid reducing agent from the tuyere provided on the furnace wall adjacent to the packed bed forming section in the lower part of the furnace to melt and reduce the powdery ore. In the case of the molten metal production method, since the fluidized bed is maintained above the packed bed of the carbon-based solid reducing agent, the distribution of the rising gas flow rate in the furnace becomes more important, and the distribution of the gas blown from the tuyere in the furnace ( It was found that if the distribution was not appropriate, the fluidization condition would partially deteriorate and the furnace operation would become unstable. When the fluidized bed becomes unstable, temperature fluctuations in the fluidized bed become large and non-uniformity of temperature occurs, resulting in partial solidification of the molten metal and slag, making it impossible to operate or changing the gas flow, Decrease, yield, and reduction rate.

In the case of a normal gas-solid fluidized bed, a dispersion plate is installed on the bottom surface of the fluidized bed to average the dispersion of rising gas into the fluidized bed. Since the temperature is high and molten metal and slag fall, it is impossible to provide such a dispersion plate.

In such a smelting reduction furnace, it is the carbonaceous material packed bed that plays the role of the dispersion plate to form the fluidized bed, and the jet depth formed by the gas blown into the carbonaceous material packed bed from the tuyere As a result, the gas dispersion state is greatly influenced, and the jet depth is extremely important for the stable operation of the fluidized bed smelting reduction furnace.

The present invention provides a method for forming a stable and uniform fluidized bed by appropriately controlling the jet depth, and efficiently smelting and reducing powdery ore.

[Means for solving problems]

The present invention maintains a packed bed and a fluidized bed of a carbon-based solid reducing agent vertically in a vertical reduction furnace, and while charging the carbon-based solid reducing agent from the upper part of the furnace, the powdery ore is mixed with oxygen to form a carbon-based solid reducing agent. Blow into the fluidized bed of solid reducing agent, and blow gas containing oxygen from the tuyere provided on the furnace wall adjacent to the packed bed forming section at the bottom of the furnace to blow into the packed bed of carbon-based solid reducing agent to melt powdered ore. In the method for producing molten metal for reduction, the jet depth of the gas blown into the packed bed of the carbon-based solid reducing agent is controlled by the following formula, which is a method for producing molten metal from powdered ore.

0.1 <J / D <0.3 where J: Jet depth of gas blown from tuyere into packed bed of carbon-based solid reducing agent (m) D: Furnace inner diameter of tuyere attachment part (m) The inventors used a device with a refractory on the furnace wall with an inner diameter of 1.2 m to form a jet depth formed above it by the gas blown from the tuyere into the packed bed of carbon-based solid reducing agent. The effect on the layers was investigated.

FIG. 1 is a schematic vertical sectional view showing a main part of a vertical smelting reduction furnace 1 main body.

The reduction furnace 1 is supplied with a carbon-based solid reducing agent from above, forms a packed bed 2 in the lower part of the furnace, and forms a fluidized bed 3 in the upper part of the furnace. The oxygen-containing gas 6 is blown from the tuyere 5 opened in the furnace wall adjacent to the No. 2 furnace. The jet injected from this tuyere is in the packed bed 2
A raceway having a jet depth J is formed on the inside of the bed, and this oxygen-containing gas burns the solid reducing agent in the packed bed, and the high-temperature reducing gas is dispersed while rising through the packed bed 2 and is fluidized gas in the fluidized bed. Becomes The powdered ore is reduced and melted by this gas, and the packed bed is dropped to collect molten iron 10 and molten slag 9 at the bottom of the furnace.

The tap hole 11 is an opening for discharging the molten metal. In addition, D in the figure shows the inside of the furnace at the attachment portion of the tuyere 5.

The appropriate jet depth J is most closely related to the furnace inner diameter D of the tuyere mounting portion at that time. Therefore, if the results in the laboratory and the results in the pilot plant are analyzed in a unified manner, it is effective for design and operation even when the inner diameter of the furnace is 3 m or more, such as an industrial scale vertical reduction furnace. .

However, in this case, it should be noted that in the case of the molten metal production method of the present invention, the powdery ore is blown into the fluidized bed of the carbon-based solid reducing agent in the upper part of the furnace together with the oxygen-containing gas, so that the powdered ore is fluidized bed. In the case of a normal gas-solid fluidized bed, since the carbon-based solid reducing agent that melts and flows in the interior is deposited on the particle surface, the weight per particle becomes heavier and the adhesiveness between particles also increases. Rather, the conditions for fluidizing gas will be more severe.

The powder iron ore used in the experiment is MBR-PB (pellet feed MBR [brand name] ore;
˜70% fine powder) was charged at 580 kg / H into a fluidized bed charged with carbon solid reducing agent.

A mixture of coke and char was used as a carbon-based solid reducing agent, and the particle size distribution was 0.5 to 20 mm, the coke was relatively coarse particles, and the char was relatively fine particles. The flow rate of oxygen blown from the tuyere was 650 to 850 Nm ³ / min, and this was blown evenly from the four tuyere.

The depth of the jet was adjusted by changing the inner diameter of the tuyere from 25 to 45 mm. Since changing the oxygen flow rate in the same tuyere system changes the heat level in the furnace, the changes in the heat level were adjusted as much as possible by adjusting the preheating temperature of the charged powdered ore, coke, char and oxygen.

The results are shown in FIG. In Fig. 2, the horizontal axis is the air flow rate,
Take the ratio J / D between the jet depth and the furnace inner diameter on the vertical axis and set the tuyere diameter 2
The cases of 5, 30, and 45 mmφ are shown. Here, J is the jet depth (m) measured by observation, and D is the furnace inner diameter (m). The jet depth was measured as the distance from the tip of the tuyere to the packed bed by inserting a gold rod into the raceway from behind the tuyere after the test operation under the same conditions was completed. From the observation inside the furnace through the peephole on the top of the furnace, the flow condition was good in the J / D range of 0.1 to 0.3, which was entered as the section where the flow condition was good in the figure.

When J / D is 0.3 or more, the central flow of the fluidized bed is too strong and blow-through occurs in the central part of the fluidized bed, making the fluidized bed unstable and
When the ratio is less than 0.1, the fluidization of the center is poor, and the operation becomes unstable in both cases. When the J / D was controlled to be more than 0.1 and less than 0.3, a stable and uniform fluidized bed could be obtained, and the most preferable condition was J / D = 0.2 to 0.25.

〔The invention's effect〕

Stability of the fluidized bed by controlling the jet depth of the blowing gas in the method for producing molten metal from powdered ore by forming a fluidized bed above the packed bed of carbon-based solid reducing agent and above it Is obtained and the operation can be stably performed for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a vertical reduction furnace to which the present invention is applied,
FIG. 2 is a graph showing the experimental results. 1 ... Vertical reduction furnace, 2 ... Packing bed of carbon-based solid reducing agent,
3 ... Fluidized bed of carbon-based solid reducing agent, 4 ... Powdered ore, 5
...... Tuyere, 6 ... Oxygen-containing gas, 9 ... Molten slab,
10 …… Melted pig iron, 11 …… Leading tap, J …… Jet depth,
D …… Inner diameter of the tuyere attachment

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoru Ikawa 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Shinobu Takeuchi 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. Research headquarters (72) Inventor Kazuhiko Sato 1 Kawasaki-cho, Chiba-shi, Chiba Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Takashi Ushijima 1 Kawasaki-cho, Chiba, Chiba Technical Research Division, Kawasaki Steel ( 56) References JP-A-59-133307 (JP, A)

Claims (1)

[Claims] 1. A vertical reduction furnace is provided with a packed bed of carbon-based solid reducing agent and a fluidized bed above it, the carbon-based solid reducing agent is charged from the upper part of the furnace, and powdered ore is mixed with oxygen. It is charged into a fluidized bed of carbon-based solid reducing agent, and a gas containing oxygen is blown into the packed bed of carbon-based solid reducing agent from the tuyere provided on the furnace wall adjacent to the packed bed forming section in the lower part of the furnace to form a powder. In the method for producing a molten metal for smelting or reducing an ore, the molten metal from a powdered ore characterized by controlling the jet depth of a gas blown into a packed bed of a carbon-based solid reducing agent within the range of the following formula Production method. 0.1 <J / D <0.3 where J: Depth of gas blown from tuyere into packed bed of carbon-based solid reducing agent (m) D: Inner diameter of tuyere attachment part (m)