JPS6247941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an apparatus for producing molten metal by pre-reducing powdery ore containing metal oxides and then melting the ore, in which the pre-reduced ore is introduced from the pre-reduction furnace to the smelting-reduction furnace. This relates to a device for

In recent years, ore raw materials containing various metal oxides have decreased in the form of lumpy ores and have become more powdery or small-grained ores, and the proportion of powdery ores will continue to increase in the future. Conventionally, binders and carbonaceous materials were added to powdery ore to process it into pellets and sintered ore and use it as agglomerates, but this not only required extra resources and energy for agglomeration. However, when firing is required, there is a drawback that the cost for treating NOx, SOx, dust, etc. in the gas discharged from the firing furnace is large.

Furthermore, when smelting is carried out in an electric furnace, such as in the production of ferrochrome by smelting chromium ore, the electricity consumption rate reaches several thousand KWH/t, making the cost extremely high in areas where electricity is expensive.

In view of the above circumstances, the present inventors have developed a method for producing molten metal by directly using powder ore without agglomerating it and producing molten metal without using electricity. We have developed and proposed a method in which the pre-reduced material is blown into a vertical melting reduction furnace together with high-temperature air through the tuyere, and melted and reduced (Japanese Patent Application No. 1983-63294).

The present invention relates to a smelting reduction apparatus comprising a pre-reduction furnace and a smelting reduction furnace, and a device for transferring and blowing granular pre-reduced ore from the pre-reduction furnace to the smelting reduction furnace. The transfer of pre-reduced ore in the smelting reduction device must satisfy the following special conditions compared to normal powder transfer.

1. Since pre-reduced ore is discharged from the pre-reduction furnace at high temperature, phenomena associated with high temperatures must be taken into account.

2. In order to reduce the temperature drop of the pre-reduced ore, the shorter the transfer distance, the better.

3. It is necessary to branch out from the pre-reducing furnace to a number of tuyeres and distribute it evenly.

4. Since the pressure is higher at the tuyeres into which the pre-reduced ore is injected than in the pre-reduction furnace, it is necessary to prevent blockage due to the pre-reduced ore and backflow of the pre-reduced ore in the transfer pipe.

5. Since the carrier gas for injecting the pre-reduced ore is blown into the smelting reduction furnace together with the pre-reduced ore, it is desirable that the amount of the carrier gas be as small as possible.

6. Re-oxidation of pre-reduced ore during transportation can be prevented.

7. The amount of pre-reduced ore injected into each tuyere can be controlled.

8. Preliminary reduced ore in the transfer pipe becomes diluted and accidents such as tuyere blast gas blowing through the transfer pipe can be prevented.

An object of the present invention is to provide an effective device that satisfies the above special conditions and facilitates the transfer of pre-reduced ore.

To achieve the above object, the present invention is characterized in that, in a smelting reduction apparatus consisting of a pre-reduction furnace and a smelting reduction furnace, high-temperature granular pre-reduced ore is transferred from the pre-reduction furnace to the smelting reduction furnace. An introduction pipe for blowing the ore into the tuyere branch pipe of the smelting reduction furnace is connected to the lower end of the pipe, and the introduction pipe is provided with a constriction part at the tip, and a carrier gas blowing nozzle is connected to the transfer pipe in the introduction pipe. The reason is that the opening is made on the distal side from the center of the joint position.

A system showing one embodiment of a melt reduction apparatus using the apparatus of the present invention will be explained with reference to FIG.

The preliminary reduction furnace 2 is supplied with ore containing powdery metal oxides by the supply device 1 . Part or all of the high-temperature reducing gas discharged from the vertical melting reduction furnace 3 is introduced from below, and particulate flux, solid reducing agent, reducing gas, etc. are supplied from the supply port 4 as necessary. , drying, heating and pre-reducing the powder ore in a fluidized bed format. The pre-reduced ore is discharged from the discharge port 5 together with flux, passes through the transfer pipe 6 and the introduction pipe 7, and is blown into the melting reduction furnace 3 together with the high-temperature air in the tuyere branch pipe 8. The pre-reduced ore described in the present invention may be accompanied by the above-mentioned granular flux and solid reducing agent, and refers to those containing these.

Inside the melting reduction furnace 3, a packed bed is formed of a lumpy carbon-based reducing agent supplied by a supply device. The pre-reduced ore blown into the smelting reduction furnace 3 is melted inside the furnace 3 and reduced while dripping down the lower part of the furnace to produce molten metal and molten slag,
It is discharged from the furnace through the discharge port 13 in a timely manner. The present invention relates to the structure of the introduction pipe 7 for the pre-reduced ore to be transferred.

When injecting prereduced ore into a smelter reduction furnace, important issues regarding the melting of the prereduced ore within the smelter reduction furnace must be considered. If the injected pre-reduced ore is not sufficiently melted within the raceway 11 formed at the tip of the tuyere, it will rush into the carbon-based reducing agent packed bed in front of the raceway in a powder form, and the holes in this packed bed will melt. This causes clumping, making it difficult to proceed smoothly with melting reduction in the furnace. Therefore, it is necessary to smoothly melt the pre-reduced ore in the raceway. The key to smoothly melting the pre-reduced ore is to inject the most appropriate amount of pre-reduced ore to the amount of high-temperature blown air (including oxygen-enriched air) per tuyere, and to melt the excess pre-reduced ore. It is important not to inject

Even if the total amount of pre-reduced ore injected into multiple tuyeres is controlled to a predetermined amount, if the amount of pre-reduced ore injected into each tuyere varies, the amount of pre-reduced ore may be increased. At the tip of the tuyere into which pre-reduced ore is injected, the melting phenomenon cannot be carried out sufficiently, which is one of the causes of furnace malfunction. This is particularly likely to be a problem in the case of ores containing metal oxides that are difficult to melt and difficult to reduce.

The introduction pipe having the structure of the present invention is capable of controlling the amount of pre-reduced ore injected by adjusting the amount of carrier gas.

FIG. 2 shows one embodiment of the introduction tube 7. As shown in FIG. 2, an introduction tube 7 is connected to the lower end of the transfer tube 6. A constriction part 9 is provided at the tip of the introduction tube 7. The throttle section 9 is extremely effective in ensuring stability in the amount of blown pre-reduced ore and improving controllability. In the system of the fluidized bed outlet 5, transfer pipe 6, and introduction pipe 7 of the pre-reduction furnace, the constricted portion 9 at the end of the introduction pipe is the narrowest bottleneck, and controls the amount of pre-reduced ore injected.

Furthermore, in order to accurately control the amount of pre-reduced ore injected, the carrier gas supply pipe 10 is inserted into the introduction pipe 7, and the carrier gas injection nozzle is opened. It is only one example that the carrier gas is supplied in the form of the carrier gas supply pipe 10 shown in FIG. 2, and a structure in which the carrier gas is supplied through the wall of the introduction pipe 7 is also possible.

When the carrier gas is supplied through the carrier gas supply pipe 10, the pre-reduced ore filled in the transfer pipe 6 and the introduction pipe 7 passes through the constriction part 9 at the tip of the introduction pipe,
The air is blown into the blown air of the tuyere branch pipe 8 branched from the main air pipe 14. The pre-reduced ore reaches the raceway 11 in the smelting reduction furnace together with the tuyere blown air, where a smelting reduction reaction occurs.

At this time, as mentioned above, the pressure inside the tuyere branch pipe 8 is higher than the pressure at the outlet 5 of the pre-reducing furnace, so the gas flows inside the transfer pipe from the tuyere branch pipe toward the outlet 5 of the pre-reducing furnace. As it tries to blow through,
It is important to prevent this, and to prevent backflow and blockage of the powdery pre-reduced ore to ensure smooth transfer. As a result of various studies, it has been found that it is effective to locate the carrier gas inlet nozzle opening closer to the tip of the introduction pipe 7 than the center of the joint position between the transfer pipe 6 and the introduction pipe 7.

As shown in FIG. 2, the distance from the carrier gas nozzle opening to the joining position of the transfer pipe 6 and the introduction pipe 7 (with the joining position as the origin and the tip side of the introduction pipe 7 as positive) is L, and the introduction pipe If the inner diameter of 7 is D, then L/
The preferred value of D is determined by the physical properties, properties, transportation, supply conditions, etc. of the powder, and its range is O≦L/D≦10.

When L/D<0, that is, when the carrier gas blowing nozzle is opened at a position farther from the tip of the introduction tube 7 than the joining position of the transfer tube 6 and introduction tube 7, a part of the carrier gas will noticeably flow inside the transfer tube 6. This backflow prevents smooth transfer of the pre-reduced ore in the transfer pipe 6, and in extreme cases, the powdery pre-reduced ore in the transfer pipe becomes diluted, preventing the blow-through of the blown air in the tuyere branch pipe 8. cause

In addition, when L/D>10, the transport capacity of the carrier gas for pre-reduced ore decreases, and there are many cases where the pre-reduced ore becomes clogged near the joint between the transfer pipe 6 and the introduction pipe 7, making it unsuitable. It is.

In addition, in general handling of powder,
Although a feeder having a mechanical structure is used to control the amount of injection, it is not advisable to use these methods in the present invention because it is necessary to transport the extremely high temperature pre-reduced ore.

Note that it is also possible to install a shutoff valve 15 for emergency use in order to stop the blow-by phenomenon of the blast gas in the transport pipe.

Next, a specific example using the device of the present invention will be given and the effects will be explained.

Example 1 Melting reduction furnace inner diameter 1.2m 2 Pre-reduction furnace inner diameter 1.1m 3 Blower tuyere 4 upper tier (powder injection) 4 lower tier 8 in total 4 Air flow rate 1200Nm ³ /hr 5 Transfer pipe inner diameter 25mm Introductory pipe inner diameter (D) 25mm Distance from the joint position of the transfer pipe with the inlet pipe to the inlet of the carrier gas (L) 75mm L/D 3 6 Carrier gas type N ₂ Using the above test furnace, powdered chromium ore (average We operate ferrochrome smelting operations from powdered iron ore (average particle size 0.2 mm) and pig iron smelting operations from powdered iron ore (average particle size 0.37 mm), ensuring stable preliminary reduction from the pre-reduction furnace to the smelting reduction furnace. It was possible to transport and inject ore. The method of the present invention is, of course, effective for various ores, not limited to the ores of this embodiment.

The effects of the present invention as described above can be summarized as follows.

1. The fluidized bed preliminary reduction furnace and the smelting reduction furnace can be connected with each other with good controllability through multiple transfer pipes and introduction pipes.

2 Pre-reduced ore does not flow back even though the pressure in the smelting reduction furnace is higher than the pressure in the pre-reduction furnace.

3. The pre-reduced ore is transferred through the transfer pipe by gravity, and is blown only in the introduction pipe section with the aid of carrier gas, so smooth injection of the pre-reduced ore can be achieved with a very small amount of carrier gas.

4. Pre-reduced ore can be injected into the smelter reduction furnace at higher temperatures due to the small amount of carrier gas required.

5. By adjusting the flow rate of the carrier gas, it is easy to distribute a predetermined amount of pre-reduced ore to each tuyere.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a melting reduction apparatus, and FIG. 2 is a partial sectional view of an embodiment of the present invention. 1...Powdered ore supply port, 2...Preliminary reduction furnace, 3...
Melting reduction furnace, 4... Supply port for powdery flux, solid reducing agent, reducing gas, etc., 5... Pre-reduction furnace outlet, 6... Transfer pipe, 7... Introducing pipe, 8... Tuyere branch pipe, 9
...Introduction pipe tip constriction part, 10...Carrier gas supply pipe, 1
DESCRIPTION OF SYMBOLS 1... Raceway, 12... Solid carbon-based reducing agent supply device, 13... Molten metal and molten slag discharge port, 1
4...Blower main pipe, 15...Shutoff valve.

Claims (1)

[Claims] 1. In a pre-reduced ore transfer/injection device in a smelting reduction apparatus consisting of a pre-reduction furnace and a smelting-reduction furnace, the ore is placed at the lower end of a transfer pipe that transfers high-temperature granular pre-reduced ore from the pre-reduction furnace to the smelting-reduction furnace. An inlet pipe for blowing into the tuyere branch pipe of the melting reduction furnace is connected, and the inlet pipe is provided with a constriction part at the tip, and a carrier gas blowing nozzle is connected to the tip of the inlet pipe from the center of the joining position with the transfer pipe. A device for transferring and blowing pre-reduced ore, characterized by having an opening on the side.