JPS58217615A - Prereducing oven in melt reducing apparatus - Google Patents

Abstract

PURPOSE:To hold a fluidized bed under an excellent condition for improving the ratio of prereduction, by forming an annular slit comprising inner and outer cylinders at the bottom of the titled oven, and providing a dispersing plate at the upper surface of the inner cylinder to sufficiently disperse supplied reducing gas. CONSTITUTION:At the bottom of the prereducing oven 1, an annular slit 6 comprising a double cylindrical tube constituted by inner and outer cylinders 10, 11 having bottom plates 12, 13 is formed and opened to the interior of the oven 1. A gas-dispersing plate 7 is provided at the upper surface of the inner cylinder 10 to supply low-temp. reducing gas to the inner space through a supply opening 8. On the other hand, high-temp. reducing gas is supplied through a supply opening 5 provided at the outer cylinder 11 to the interior of the annular slit 6. Inside the prereducing oven 1, the fluidized bed of a powdery ore is formed by the mixture of the high and low-temp. reducing gases. By this gas-supply mechanism, the introduced gases can be uniformly dispersed, and the fluidization of particles at the central part of the oven 1 can be satisfactorily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used in a method for producing a molten metal by pre-reducing a powdery ore containing a metal oxide and then melting and reducing the ore. It relates to a preliminary reduction furnace in a smelting reduction apparatus comprising a preliminary reduction furnace and a smelting reduction furnace connected in series,
Preferably, the present invention relates to a preliminary reduction furnace in the smelting reduction apparatus for producing ferrochrome.

In recent years, ore resources containing metal oxides have tended to be of lower grade and become finer minerals. The production of ferroalloy by smelting ore is usually done using an electric furnace, but the electric power consumption is several thousand kilowatts.
H/t, resulting in extremely high costs.

Recently, the smelting reduction method has been attracting attention as a technology for producing ferrochrome and other ferroalloys that does not rely on electric power. The present inventors previously proposed a method for producing molten metal from powdery ore using a device in which a preliminary reduction furnace and a smelting reduction furnace were connected in series, and this method can be applied to the smelting of various ores. It is.

Accordingly, the method utilizes the high temperature exhaust gas of the smelting reduction furnace as a source of the reducing agent and heat necessary for preliminary reduction of ore containing metal oxides. The pre-reduction furnace is of a fluidized bed type because it uses powdered magnets directly without agglomerating them. It is known that dispersion of the introduced gas is important in order to obtain a good fluidization state in the fluidized bed, and it is especially important when high temperature exhaust gas is introduced into the pre-reduction furnace as in the smelting reduction method. It is. Regarding the dispersion of the introduced gas, the gas dispersion means of the preliminary reduction furnace must have the following functions.

/) #It is possible to introduce high temperature reducing gas of 1000-/7θO°C from the fusion furnace.

h) Not easily affected by large amounts of fine dust in high-temperature exhaust gas.

3) Uniform distribution of gas within the furnace is possible.

D) The gas concerned and other introduced gases are sufficiently mixed.

As means for dispersing the introduced gas in a conventional general fluidized bed type furnace, there are methods as shown in FIG. 1 (a), (b), and (c).

Powder-like particles are charged into a vertical fluidized bed furnace/ψ, and the particles are fluidized by the gas introduced from the inlet gas supply port/7 to form a fluidized bed/S. Introduced gas into fluidized bed
(a) to disperse it uniformly within S.

A gas distribution plate/6 is usually provided as shown in the fluidized bed F/4t (0). Examples of gas distribution plates include perforated plates, sintered plates, and valve cap type plates.

However, when the conventional furnaces (a), (b), and (c) are used as a preliminary reduction furnace of a melting reduction apparatus, the following problems arise.

In other words, since the furnaces (a) and (b) are equipped with a gas distribution plate, the introduced gas can be uniformly dispersed.

There are problems with the material and strength of the gas distribution plate due to high-temperature gas of 1000° C. or higher, and problems with clogging due to fine dust. Further, since the furnace (c) is not provided with a gas distribution plate, the problems in (a) and (b) above do not occur, but there is a problem in uniformly dispersing the introduced gas. Furthermore, in each of (a) to (c), the mixing with other introduced gases is insufficient.

Therefore, an object of the present invention is to solve the above-mentioned problems in the preliminary reduction furnace of the conventional smelting reduction apparatus, so that the reducing gas can be sufficiently dispersed and the fluidized bed can be formed effectively. An object of the present invention is to provide a pre-reduction furnace, preferably for the production of ferrochrome, equipped with means.

That is, the gist of the present invention is as follows.

In a smelting reduction apparatus consisting of a pre-reduction furnace and a smelting reduction furnace, the pre-reduction furnace is connected by an inner and outer double coaxial cylinder such that an inner cylinder and an outer cylinder form an annular slit opening into the pre-reduction furnace. A gas dispersion plate is provided on the upper surface of the inner cylinder, a high temperature reducing gas supply port is provided in the nuclear outer cylinder, and a low temperature reducing gas supply port is provided in the inner cylinder. A preliminary reduction furnace in a smelting reduction device.

The present invention will be explained in detail below.

The outline of the preliminary reduction furnace of the present invention is shown in FIG. 1 in its longitudinal section. The pre-reducing furnace/ is vertical and has a feed port for raw materials such as powder and granular ore containing metal oxides such as chromium ore and flux on the approximately central side wall.3. A discharge port 9 for pre-reduced ore is provided, and a discharge port 9 for exhaust gas during pre-reduction is provided on the upper side wall.

The bottom of the furnace is formed by a bottom plate 2. The inner cylinder 10 has an inner cylinder 10 and an outer cylinder 10 having a diameter of 1/3 and an outer cylinder 10 having a diameter of 1/3. The inner cylinder 10 is provided with a low-temperature reducing gas supply port opening into the inner cylinder space, and the outer cylinder l/ is provided with a high-temperature reducing gas supply port S opening into the annular slit 6. There is.

A fluidized bed λ of granular ore is formed in the preliminary reduction furnace/by a mixed gas of high temperature reducing gas and low temperature reducing gas introduced into the bottom of the furnace.

As mentioned above, raw materials such as ore and flux are supplied from the supply port 3, and pre-reduced ore is discharged from the discharge port q.
Transferred to a melting reduction furnace. High temperature reducing gas from the melting reduction furnace is introduced from the supply port S. In the case of pre-reduction of chromium ore, supplying a CH4-containing gas such as coke oven gas will significantly accelerate the pre-reduction reaction rate, so it can be supplied at a lower temperature than smelting reduction furnace exhaust gas like coke oven gas. The gas is introduced from the supply port t and into the fluidized bed λ via the gas distribution plate 7. The preliminary reduction furnace exhaust gas is discharged from the discharge port t.

By the way, in order to improve the fluidization state of the fluidized bed,
It is said that it is best to make the pressure loss of the gas in the gas distribution plate 10% or more of the Q pressure loss in the fluidized bed. 1000 to 100℃ for perforated plates and bubble cap type gas distribution plates
Introducing high-temperature gas causes problems in terms of material quality and strength, and in sintered plates, the ducts in the high-temperature gas cause clogging. In the type shown in FIG. 1(c) that does not use a gas distribution plate, the pressure loss is too small to obtain a good fluidization state.

Therefore, in the pre-reducing furnace of the present invention, the bottom of the furnace has a coaxial double inner and outer cylinder structure (IO, U), thereby providing an annular sulin (A) for introducing high temperature reducing gas on the circumferential side of the bottom of the furnace. These problems were solved by installing a gas dispersion plate for introducing low-temperature gas at the center of the bottom of the furnace.

That is, according to the present invention, by appropriately selecting the slit width in the annular slit, it is possible to easily obtain the pressure loss necessary for gas dispersion to effectively form a fluidized bed, and Since the slit portion can be easily constructed from a refractory material or a heat-resistant metal material, there is no risk of problems with the material of the slit portion or clogging.

In addition, a commonly used gas distribution plate can be used as the gas distribution plate installed in the center, thereby making up for the lack of fluidization in the center of the furnace. Furthermore, since both gases can be introduced from the bottom of the fluidized bed, one can be introduced from the bottom,
Both gases are better mixed than when the other is introduced from the side wall.

Next, examples of the present invention will be shown.

Prereduction furnace fluidized bed inner diameter /,, 27Fl Furnace bottom outer cylinder inner diameter o, sm Annular slit width 30mm Type of gas distribution plate Porous plate High temperature reducing gas supply port inner diameter 3ooIII Low temperature reducing gas supply port inner diameter 10OIB Above prereduction furnace Powdered chromium ore was pre-reduced using a test furnace as described below under the conditions shown below. In this test, by using a pre-reduction furnace equipped with a means for dispersing the introduced gas according to the present invention, it was possible to introduce high-temperature gas into the pre-reduction furnace without causing the problems that occur in conventional furnaces. Therefore, the fluidized bed could be formed well.

l) Chromium ore: Composition of chromium ore from the Philippines: (1
! r203M9.24 FeO23,g Chi particle size Hst-1IgMq, q% lIt~100M K4.7% 100M or less 5. Hirochi (M stands for mesh) Co) Pre-reduction furnace operation data Chromium ore supply amount: /zao kl? / hr Amount of smelting reduction furnace exhaust gas as high-temperature gas: A10 N m'! s/hr
Gas temperature: /3 0°C Amount of coke oven gas as low temperature gas: /5 N 7H3/hr Gas temperature near 0°C Pre-reduction furnace temperature: 1020°C Preliminary reduction rate of chromium ore: For test examples of 37 or more On the other hand, in the conventional test method using the capacity shown in (a) and (b) in Figure 1, the gas distribution plate was deformed by the heat from the high-temperature gas, making long-term operation impossible. . Although the furnace method (c) could be operated, a good fluidization state could not be obtained and the preliminary reduction rate was extremely low.

The effects of the preliminary reduction furnace of the present invention are summarized as follows.

/) Since a gas dispersion plate is not used at the introduction part of the high temperature reducing gas, there is no problem with the strength of the material of the dispersion plate.

2) The annular slit allows the introduced gas to be uniformly dispersed.

3) Other low-temperature reducing gases can be introduced through the gas distribution plate attached to the center.

t) The particles in the central part of the furnace can be fluidized well.

S) The introduced high-temperature gas and other introduced gases can be sufficiently mixed.

[Brief explanation of drawings]

(A), (B), and (C) in FIG. 1 are schematic vertical cross-sectional views of the lower part of the furnace, respectively, for explaining the mode of dispersion of introduced gas in a conventional fluidized bed furnace. The figure is a schematic longitudinal sectional view showing one embodiment of the present invention. /...Preliminary reduction furnace, Co...Fluidized bed, 3...Ore,
Supply port for flux, etc., pre-reduced ore discharge port. 5...Inlet for high temperature reducing gas, 6...Annular slit, ? ... Gas distribution plate, S ... Inlet for low-temperature reducing gas, 10 ... Inner cylinder, / C ... Outer cylinder, l Co ... Bottom plate of inner cylinder, 13 ... Outer cylinder Bottom plate, / da... fluidized bed furnace,
15-... Fluidized bed, /6... Gas distribution plate, /7...
Fluidization gas inlet. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] L In a smelting reduction apparatus consisting of a pre-reduction furnace and a smelting reduction furnace, the pre-reduction furnace is connected to the pre-reduction furnace by an inner and outer double coaxial cylinder such that an inner cylinder and an outer cylinder form an annular slit opening into the pre-reduction furnace. A gas dispersion plate is provided on the upper surface of the inner cylinder, a high temperature reducing gas supply port is provided in the nuclear outer cylinder, and a low temperature reducing gas supply port is provided in the inner cylinder. A preliminary reduction furnace in a smelting reduction apparatus, characterized by: