JPS5980704A - Melt reduction method of powder and granular ore by vertical type furnace - Google Patents

Abstract

PURPOSE:To perform economical melt reduction of powder and granular ore by inexpensive weakly caking coal or the like by making use of the waste reducing gas produced in a vetical furnace by melt reduction for preliminary reduction of the powder and granular ore and blowing the patially reduced iron formed by said reduction together with said wate gas into the vertical furnace. CONSTITUTION:Preheated air is blown through tuyere groups 5, 5' into a vertical furnace 3 where the packed layer of coke, etc. is fired and part of the reducing waste gas 6 generated by such firing is supplied 6 to the bottom of a preliminary reduction furnace 2 to heat and reduce preliminarily the powder and granular ore charged into the furnace 2. The partially reduced ore formed by such reduction is blown together with the preheating air particularly through the tuyere group 5 near the upper stage and further through the tuyere group 5' into the furnace 3. The partially reduced iron blown together with the preheating air in the high temp. region formed in the furnace 3 is immediately heated and is easily melted. While such reduced iron drops toward the lower part of the furnace 3, the iron is reduced to form a molten metal and molten slag, whereby the smelting is accomplished. The molten metal accumulating in the hearth is removed through a tapping hole 10 to the outside of the furnace at a proper time. The molten slag is treated in a similar way.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for smelting and reducing ore in the form of powder and nine granules in an oven type furnace, and in particular, it is advantageous and appropriate to use reducing exhaust gas generated in an electric furnace by melting reduction for the preliminary reduction of one ore in the form of powder and one granule. The present invention discloses the development results for particularly effectively accomplishing the smelting reduction of partially reduced ore that has undergone preliminary reduction in a vertical furnace.

In recent years, the raw material ores mainly composed of various metal oxides, including iron ore, have become more powdery and granular ores rather than lumpy ores, and the proportion is expected to continue to increase in the future. powder.

As a smelting method using granular ore, a fluidized bed is used to smelt powder 9.
A common method is to pre-reduce granular ore and melt and reduce the pre-reduced ore in an electric furnace, converter, or melting furnace in a pond.

In this case, there are many methods in which the pre-reduced ore is agglomerated by adding a binder and the agglomerated product is melted and reduced in a melting furnace. However, this method not only requires materials for agglomeration, processing costs, processing energy, etc., but also requires a large amount of energy from the kiln when firing is required after agglomeration. Another drawback is that the cost for treating NOx, SOx, dust, etc. in the emitted gas increases considerably.

In addition, a method has been proposed in which the pre-reduced ore is melted and reduced without agglomeration or calcination using an arc furnace or a furnace that uses plasma or pure oxygen in the pond of the above method. The method used not only consumes a huge amount of power, but also has restrictions on location.Also, the method using a furnace that uses plasma consumes so much power that it is currently difficult to apply on an industrial scale. Furthermore, although it is easy to obtain a high-temperature atmosphere using a furnace that uses pure oxygen, it is difficult to maintain a reducing atmosphere and the amount of oxygen used increases, all of which have problems that require technical solutions. Random.

By the way, after pre-reducing finely crushed ore, melting and reducing the pre-reduced ore by heating with a coal/oxygen burner was disclosed long ago in Japanese Patent Publication No. 34-2103. Some of the inventors have previously proposed an improved method for identifying and reducing the carbon content by melting and reducing it only by introducing oxygen.
The proposal was made in Publication No. 44925, but the former uses powdered coal as a fuel and reducing agent to melt and reduce the pre-reduced ore, and the latter uses reduced iron-adhered carbon, and uses room temperature as a combustion aid for combustion. It uses oxygen.

In response to this, the inventors went further and continuously formed a packed layer of carbonaceous solid reducing agent inside the vertical furnace, while at the same time forming a plurality of tuyeres in two stages, upper and lower, on the lower body wall of the electric furnace. Partially reduced ore, which is obtained by pre-reducing powder ore and granular ore using reducing exhaust gas discharged from an electric furnace, is heated with high-temperature air at 800 to 1800°C or oxygen-enriched air, adding flux if necessary. The invention of Japanese Patent Application No. 56-63294 was previously proposed for melting and reducing the above partially reduced ore by blowing it into a vertical furnace under air flow conveyance.

Regarding this, further development research is being carried out on an industrial scale, but at this stage we are conducting the above-mentioned blowing experiment using airflow conveyance of partially reduced ore, and by increasing the blowing flow rate of the airflow, Even when low-temperature oxygen-containing gas or oxidizing gas is used in the PZ, the required amount of heat for the preliminary reduction furnace can be sufficiently satisfied by increasing the amount of exhaust gas from the vertical furnace. Hot blast stove fuel can be replaced by simple means such as sensible heat recovery and utilization through heat exchange with vertical furnace or pre-reduction furnace exhaust gas without requiring the addition of large-scale facilities such as regenerative hot blast stoves. What's more, the increase in exhaust gas from vertical furnaces can be eliminated! It has been found that the entire amount can be used advantageously as a by-product gas on the way up, and therefore the temperature range of the reactive gas injected into the vertical furnace is expanded to the lower temperature side, to about 800°C. (I focused on the favorable situation and proceeded to consider it.) By setting the number of tuyere groups to 8 or more, it is possible to prevent partially reduced ore from being reducible or dissolvable. It has been found that smoother smelting reduction can be achieved advantageously in a vertical furnace, including in cases where

That is, in this invention, the pre-reduced ore of one powder ore is added as necessary through tuyeres arranged in multiple stages at the lower part of the barrel wall of a vertical furnace in which a packed bed of carbon-based solid reducing agent is formed. The flux is blown into a vertical furnace using a heated reactive gas stream and melted and reduced.
By using the reducing exhaust gas generated by smelting reduction in a vertical furnace for preliminary reduction of one-grain ore powder, we can appropriately overcome the problems in the conventional method of smelting two-grain ore powder. It has been accomplished.

In this invention, conveying by a reactive gas stream under preheating,
The charge that is blown into the vertical furnace from the tuyere group drips into the high-temperature region of the packed layer of carbon-based solid reducing agent formed inside the vertical furnace around the tip of the tuyere. During this process, it is melted down and accumulated in the hearth, so it can be removed from the vertical furnace at the appropriate time.

In this invention, lump coke with a particle size of about 25 to 75 mm is particularly preferably used as the carbon-based solid reducing agent, but coal lumps, char, etc. can also be used. It is continuously supplied to continuously form a filled layer.

Next, in a pre-reduction furnace, the powdery two-granular ore is subjected to fluidized bed reduction, preferably in face-to-face contact with the reducing exhaust gas emitted from the furnace. M.B.R.
Ores such as chromium ore from the Philippines and manganese ore from Australia can be used as they are, or if necessary, those that have been granulated according to conventional methods can be used.

Partially reduced ore may be mixed with flux such as limestone, silica dolomite, or serpentine depending on the type and shape of the ore, or mixed particles of 2 powder ore and 7 lux in the above granulation process. After pre-reduction is performed as follows, the reactant gas is blown into a vertical furnace with a preheated reactive gas stream and melted and reduced.

The reactive gas stream under heating is blown into the vertical furnace, and recovers sensible heat by heat exchange with the reducing exhaust gas generated in the pre-reduction furnace. Preheat to temperature or further 1800° if required
It is used by heating it in a normal gas heating furnace to a humidity of about C. In any case, reactive gases, such as oxygen-containing gases such as air, oxygen-enriched air (oxygen content of less than 50%), and other oxygen-argon mixtures, pose problems for ventilation piping in the above temperature range. Oxidizing gases that do not produce oxidizing gases can be used.

In this invention, pre-reduced ore is blown into the vertical furnace using a reactive gas stream while preheating is performed at least in the upper row group, and the row groups are arranged in multiple upper and lower stages to melt the ore. The reduction reaction can be maintained stably.

The partially reduced ore is one that has been pre-reduced with the exhaust gas of a vertical furnace of powdered nine-granule ore, and preferably one that has been reduced in a fluidized bed is suitable for practical use.

FIG. 1 schematically shows a smelting reduction system suitable for carrying out the present invention, in which 1 is a supply device for powder and granular ore, 2 is a preliminary reduction furnace, and 8 is a vertical furnace used for smelting reduction. 4 is electric furnace 3
5, 5', and 5' are vertical furnaces in this example. This is a group of tuyere in which multiple tuyeres are arranged in eight upper and lower stages at the bottom of the 81st circumference of 8.

By blowing, for example, air under heating through this panel group 5s 5', 5', the packed layer in the vertical furnace 8 is ignited, and the reducing exhaust gas generated in the vertical furnace 3 is removed. A part of the ore is led from the exhaust port 6 to the bottom of the pre-reducing furnace 2 through a branch pipe 6', and the powder and two granular ores charged into the pre-reducing furnace 2 are dried, heated and pre-reduced. The partially reduced ore thus preliminarily reduced is fed from the ore discharge lower to the feed ore If7 shown by the broken line.
′, especially the upper row of feathers group 5, or further 5
', and is blown into the mold furnace 8 together with preheated air. At this time, in order to facilitate the transfer of the partially reduced ore in the feed pipe 7', a part of the exhaust gas in the branch pipe 6' is transferred to the booster 8.
It is advantageous to pressurize and thereby assist the transport.

The preheated air blown into the vertical furnace 8 is 800 to 1800°C.
Preferably, if necessary, a gas heating furnace is used and the exhaust gas is preferably introduced into a heat exchanger that recovers the sensible heat of the exhaust gas from the vertical furnace 8 or the pre-reduction furnace 2. If the air is preheated, operating costs will be extremely low.

In order to blow partially reduced ore into the vertical furnace a using preheated air, the upper panel group 5 or further 5' is used,
Although not shown in the figure, 7
It is preferable that lux is also simultaneously blown in from the tuyere group 5 or further 5', and only preheated air is blown into the lower tuyere group 5'.

The packed layer thus formed in the vertical furnace 8 generates a raceway near the tip of the tuyere similar to that at the tip of the tuyere of a blast furnace, forming a high-temperature region, into which the preheated air is blown. The reduced ore is immediately heated and easily melted, and while dropping into the lower part of the vertical furnace 3, it is reduced to produce molten metal and molten slag, and smelting is performed. The molten metal accumulated in the hearth is taken out of the furnace from the tap lO in a timely manner.

The same applies to molten slag.

The area around the raceway that forms the high-temperature region of the packed layer is in the combustion atmosphere of the lumpy carbon-based reducing agent, and the oxygen content is low, that is, the oxygen partial pressure is low. The reduction of the partially reduced ore melted in the raceway section is carried out very favorably.

In this invention, lump coke is suitable as the carbon-based solid reducing agent, but lump coke or coal may be used instead, or they may be used in combination.

The vertical furnace 8 can be built at a much lower temperature than a normal blast furnace, which makes it convenient for operation.In particular, the partially reduced ore can be introduced into the furnace through the tuyere 5, 5' at the bottom of the trunk wall of the vertical furnace 3. Since it is supplied by injection, there is no need for a strong reducing agent as in blast furnaces, and therefore weak or non-caking coal can be used instead of expensive highly caking coal, making it economically advantageous. be.

In addition, the partially reduced ore is heated in the raceway section by the heat of reaction between it and oxygen in the heated air, and the retained heat is brought into the vertical furnace 8 under the environmental temperature in the preliminary reduction furnace 2. Therefore, it is advantageous.

Although the preliminary return rate is not constant depending on the type of ore etc., it is 80
The best results can be obtained within the range of ~80%.

In this invention, the tuyere groups 5, 5', and 5' are arranged in eight upper and lower stages because the partial reduction furnace is blown into the furnace together with preheated air through these tuyere groups or the tuyeres 5 or 5'. If the amount of heat required for melting and reduction near the tuyere tip is insufficient, even if melting occurs near the tuyere tip, there will be insufficient heat replenishment on the way to the bottom of the furnace, inhibiting reduction. This is to eliminate the risk of not being able to operate smoothly due to cooling of the hearth, and in this sense, partially reduced ore is mainly supplied from the upper side group 5 or further 5', and the partially reduced ore is supplied from the lower side group 5'. Therefore, it is desirable to heat the hearth part to a high temperature to ensure the amount of heat necessary for reducing the molten material dripping there.

Example 1 The experiment was carried out in a test reactor according to the system system shown in FIG. The results are shown below.

1) Brand of chromium ore: Particle size of chromium ore from the Philippines:
0.4 state supply amount: 40219/hr 2) Type of carbon-based solid reducing agent, coke particle size: 20-4
011+11 Supply amount: 6oxIc9/hr 8) Vertical furnace air flow rate: 1440 N111”/h
r Blow temperature: 950”C Blow tuyere: 4 each for upper, middle and lower tuyere, 12 in total (partially reduced ore is supplied to 8 upper and middle rows) Preliminary reduction rate: 87% 4) 7xorium production amount: 230 J9/ hr composition:
Gr54.9%C6,7%Si5.9%5 Slag discharge amount: aaakg/hr Example 2 The same test results as Example 1 are shown below.

1) Manganese ore brand: Australian manganese ore particle size: 11111 or less Supply amount: 472 kg/hr 2) Type of carbon-based solid reducing agent, coke particle size: 20-4
0 Seagull supply amount: 4021c9/hr 8) Air blowing to vertical furnace 4171510 Nm'/hr
Blow temperature: 2000℃ Blow tuyeres: 4 each for upper, middle and lower tuyere, total 12 (Partially reduced ore is supplied to 8 upper and middle rows) Preliminary reduction rate = 54% 4) Ferromanganese production amount: 2601c9/hr Composition:
) 4n75.8%C7,4%SiX, 6%5) Slag discharge amount: 22O2Ic/hr According to this invention, it is not necessary to use expensive electricity, and it is not necessary to use strong coking coal, but relatively cheap weak coal. Only a small portion of the reducing exhaust gas generated in a vertical furnace in which a packed layer of carbonaceous solid reducing agent is formed using coking coal or non-caking coal can be effectively used for preliminary reduction of ore. Instead, it is possible to achieve particularly smooth and stable smelting reduction of partially reduced ore in a vertical furnace, so there are great expectations for the future method of smelting single-grain ore, which is concerned about rising energy costs in recent years. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the system system of the present invention. Patent applicant: Kawasaki Steel Corporation Figure 7 Continuation of page 1 0 shots clear person Tsutomu Fujita Kawasaki Steel Co., Ltd., 1 Kawasakicho, Chiba City Ceremony company Chiba Works 0 shots by Shunji Hamada Kawasaki Steel Co., Ltd., 1 Kawasakicho, Chiba City Ceremony company Chiba Works 37-

Claims (1)

[Scope of Claims] L A packed layer of a carbon-based solid reducing agent is continuously formed in a vertical furnace, while being heated through a plurality of groups of panels arranged in multiple stages in the upper and lower parts of the lower part of the shaft wall of the shaft furnace. Partially reduced ore obtained by pre-reducing two granular ores by injecting a reactive gas of is introduced and charged into the vertical furnace along with the blown gas airflow.
A method for melting and reducing powder and granular ore in a furnace, which comprises stabilizing the melting and reducing environment in the hearth by blowing gas airflow from a group of tuyeres on the lower stage. 2. The method according to item 1, wherein the heated reactive gas is blown through a plurality of groups of panels arranged in eight or more upper and lower stages at the lower part of the trunk wall of the vertical furnace.