JPS58193330A - Preliminary reducing method and apparatus for reducing chromium ore by melting - Google Patents

Abstract

PURPOSE:To enhance the preliminary reducing efficiency of a Cr ore, in the solid phase preliminary reduction of the Cr ore, by breaking a spinel type structure by preliminary oxidation treatment of said Cr ore. CONSTITUTION:In preparing ferrochromium in a melting and reducing furnace after a Cr ore is preliminarily reduced, the preliminary reduction of the Cr ore is enhanced to reduce refining cost of ferrochromium. For obtaining this effect, the Cr ore is crushed to be charged into an oxidation treatment furnace 1 from the inlet 3 thereof and the fluidized layer 2 of the powdery Cr ore is formed therein. Oxygen or air is introduced into the oxidation treating furnace 1 from the lower inlet 5 thereof and the high temp. exhaust gas from a ferrochromium melting and reducing furnace from an inlet 8 while the high temp. of a preliminary reducing furnace 10 provided to the lower part is further introduced through a conduit and a dispersing plate 9 to heat the Cr ore and the spinel structure of the Cr ore is broken to separate FeO from Cr2O3. This Cr ore made easily reducible is charged into the lower preliminary reducing furnace 10 by a transfer pipe 4 while a reductive gas 18 such as a coke oven gas is introduced to preliminarily reduce the Cr ore in a solid phase in an excellent reducing ratio and the reduced ore is supplied to the melting and reducing furnace to prepare molten ferrochromium.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preliminarily reducing chromium ore when smelting and reducing chromium ore for the purpose of producing 7-erochrome.

Chromium ore resources are trending toward lower grade and fine mineralization. The production of chromium 7 by smelting chromium ore is usually done using an electric furnace, but the electricity consumption rate reaches several thousand kilowatts per ton, making it extremely costly in areas where electricity rates are high.

Therefore, recently, the smelting reduction method has been attracting attention as a technology for producing 7-erochrome and other ferroalloys that does not rely on electric power.

Regarding this smelting reduction method, the present inventors previously invented a method for producing molten metal from powdery ore (Patent Application Sho! 4-AJ
Kodeda). The gist of the invention is that granular ore is preliminarily reduced in a fluidized bed format using reducing gas discharged from the smelting reduction furnace in a pre-reducing furnace, and the resulting granular pre-reduced ore is placed in upper and lower stages, respectively. The pre-reduced ore is transferred to a vertical smelting reduction furnace equipped with a plurality of tuyeres, and is blown into the smelting reduction furnace together with high-temperature air through at least the upper tuyeres of the tuyere to melt and reduce the pre-reduced ore. This is a method for producing molten metal from powder ore containing metal oxides.

This method is applicable to various ores, and can naturally be applied to the production of 7-nirochromium from chromium ore.

However, ores that are difficult to reduce, such as chromium ore, require a very high reduction temperature when using high-temperature exhaust gas from a smelting reduction furnace as reducing gas.

The present inventors have proposed a method using a reducing agent such as heavy oil or coal as a preliminary reduction method for chromium ore using a fluidized bed (Special Application of Akio!).
! r-1047/7), and discovered that OH2 is effective as a reducing agent when reducing at a lower reduction temperature. Gansho! A-/97 Code No. 6) was proposed.

From the two methods proposed above, it has been found that in order to speed up the reduction rate of chromium ore, it is effective to select a reducing agent and, if the reducing agent is the same, to increase the reduction temperature.

On the other hand, it is also possible to improve the reduction rate by changing the properties of the chromium ore itself. Chromium ore has a spinel crystal structure (Fe2Mg)0.(Or +
kl ) 203. In the spinel crystal, F@oxide (Fed) and Or oxide (0rzO3
) is reduced, but because it has a spinel structure, the reduction rate is slower than when FeO and Gr203 are reduced as a mixture.

Therefore, by breaking the spinel type #I structure, yIO and 0rz0
If treatment is performed such that 5 is separated, an increase in the reduction rate can be expected.

Furthermore, since chromium ore is dense, the reducing gas penetrates into the interior of the ore particles and becomes entangled, which also slows down the reduction rate.

The reduction rate can be increased by generating a porous structure or a large number of tartars to increase the size of the pores within the particles.

Therefore, as a means to achieve the above objective, chromium ore is added to a high temperature oxidizing atmosphere in advance! The present invention was developed based on the idea of performing oxidation treatment by exposing the material to air.

The present invention provides a method for pre-reducing chromium ore that can improve the pre-unity ratio of chromium ore in a smelting-reduction method for difficult-to-reducible chromium ore for producing 7 Ewak Tam, and an implementation of the method. The purpose is to provide an apparatus for use.

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

(1) In a method of melting and reducing chromium ore using a preliminary reduction furnace and a smelting reduction furnace, powdery chromium ore is
A method for pre-reducing chromium ore, which comprises oxidizing the chromium ore with air or oxygen at a temperature of toθ to /300°C, and then supplying the oxidized chromium ore to a pre-reduction furnace for pre-reduction.

(2) A vertical oxidation treatment furnace is installed above the vertical pre-reduction furnace, and the oxidation treatment furnace includes a chrome ore supply port, an air or oxygen supply port, a pre-reduction furnace exhaust gas supply port, A transfer pipe for the oxidized chromium ore, a discharge port for the exhaust gas from the oxidation process, a 7-lux supply port and a reducing gas supply port are provided as necessary, and the preliminary reduction furnace is equipped with a reducing gas supply port. supply port,
It is characterized by providing an outlet for the pre-reduced exhaust gas and an outlet for the pre-reduced chromium ore, and communicating the oxidation treatment furnace and the pre-reduction furnace through a transfer pipe for the chromium ore and a conduit for the pre-reduced exhaust gas. A preliminary reduction device for chrome ore.

The present invention will be explained in detail below.

Figure 1 shows the bead strength of 0r203 and the effect of oxidation treatment on xm diffraction of chromium ore (-g) which was oxidized for 7 hours in an oxygen stream (300CO/win) using an annular electric furnace. This shows the relationship with temperature. According to this, as the oxidation treatment temperature increases, 0r203
The peak intensity tends to increase at /100'C, but when the temperature is further increased to exceed 1300°C, it tends to decrease.

In addition, when observing the original chromium ore and the chromium ore after oxidation treatment under a microscope, it was found that the higher the oxidation treatment temperature, the more fine racks were generated in a network shape.

Next, we conducted a reduction experiment on oxidized chromium ore using a fluidized bed reduction device. The experiment used one reaction tube,
First, oxidation treatment was performed at a predetermined temperature, followed by purging with NN2, and then the temperature was raised to a predetermined temperature to perform reduction.

The results are shown in Figure 1.

According to Figure 1, the higher the oxidation treatment temperature, the higher the reduction rate of chromium ore. However, when the temperature exceeds 7100°C, the tendency to decrease is similar to that shown in FIG. The reason why the reduction rate improves is that the spinel structure in the chromium ore is destroyed by the oxidation treatment and 0r203 is generated, and fine tartars are generated.
It is thought that the reducing gas penetrated to the center of the chromium ore particles, and reduction proceeded in parallel from the outside and inside of the particles. The reduction conditions in Figure 2 are: reduction temperature/100°C;
OE [4j 47m1n as a reducing gas, N2 as a fluidizing gas, reduction time/ko 0 min, #
It is the mamu ore - Keyaki.

When performing oxidation treatment, (1) the ore is charged into the reaction tube before the temperature rises, and (2) the ore is charged after the reaction tube has been heated to a predetermined temperature. be.

As shown in FIG. 2, method (2) is effective in improving the reduction rate. This means that because the ore was rapidly exposed to high temperatures from room temperature, the rapid heating caused more cracks to occur inside the ore than in method (1), increasing the specific surface area of the ore grains, and reducing the amount of reducing gas. This seems to be due to more active penetration into the grains. 'However, according to Figure 1 and Figure a9, the temperature of the oxidation treatment of chromium ore is
/ It can be seen that the reduction effect is improved in the first reduction step when the temperature is 300°C.

The method of the present invention applies the pre-oxidation treatment of chromium ore, which has produced clear results from the various experiments described above, to the pre-treatment of the preliminary reduction method in the smelting reduction method of chromium ore.

FIG. 3 is a 70-sheet of a pre-reduction apparatus used to carry out the method of the invention, thereby illustrating an embodiment of the method and apparatus of the invention.

A fluidized bed reactor is used as the oxidation treatment furnace.

Its shape is usually a vi-shaped cylinder. Powdered chromium ore is supplied from the supply port 3, forms a fluidized bed in the reactor, is oxidized, is discharged through a transfer pipe, and is sent to the preliminary reduction furnace IO.

Blanks are supplied from the supply lower as needed.

In the preliminary reduction furnace 10, high-temperature exhaust gas is discharged from its outlet/3
．． Exhaust gas from the furnace 73' is discharged from the furnace, while the exhaust gas from the furnace 13 passes through the conduit 6 and is supplied into the modification furnace via the distribution plate D.

-Element or air is supplied from its supply port j.

Its use is to oxidize chromium ore to break its spinel structure and produce 0r203, and also to generate fine lacs in the ore, thereby facilitating the preliminary reduction of chromium ore, and Reduction furnace exhaust gas (
00v H2t OH4) is burned to supply the heat necessary for oxidation treatment. In order to actively carry out the oxidation reaction of the chromium ore in the furnace, it is preferable that air or oxygen be in excess, so oxygen or air may also be supplied from the supply port 5/. The ratio of the amount of exhaust gas supplied from the preliminary reduction furnace 10 to the oxidation treatment furnace I, that is, the amount that enters the inlet pipe B from the discharge port 13 of the preliminary reduction furnace IO is 5 to 30% of the total amount of exhaust gas discharged. If necessary, it is also possible to supply exhaust gas from a melting reduction furnace (not shown) and other reducing gases into the oxidation treatment furnace through its supply port.

The oxidized ore supplied from the oxidation treatment furnace 1 to the pre-reduction furnace 10 through the transfer pipe Hiroshi is mixed with exhaust gas from the smelting reduction furnace supplied from the supply ports // and //' or coke oven gas from /r. Pre-reduction is carried out in a fluidized bed format with a reducing gas. The pre-reduced ore is discharged from the discharge port 1 and sent to the smelting reduction furnace.

The preliminary reduction furnace is charged with chromium ore from LDE and 7 lux from χ according to the operational needs, and it is also possible to blow 02 or air from COI to replenish the heat of the preliminary reduction furnace. .

By the way, as a method of preheating raw materials using high-temperature exhaust gas, a one-type suspension preheater is used in cement manufacturing kilns and the like.

An example in which this method is applied to the oxidation treatment furnace of the present invention is shown in sheet 70 of FIG.

Chrome ore is the first stage suspension preheater/
4I' from the supply pipe /j, and then supplied to the third stage eggplant preheater /'I via the first stage soot pump preheater /'I'. - The exhaust gas from the sumo wrestler +1 reduction furnace 10 is fed to a 112-stage suspension preheater and combusted with excess air or oxygen from the tube %/A, and the exhaust gas is fed to the first stage suspension preheater/ It is supplied to the first stage suspension preheater l' via l'.

Ritam ore is preliminarily oxidized while being suspended in the exhaust gas from the previous preheater in the first stage preheater/da' and the second stage preheater/4", and is then oxidized in the third stage preheater l. The ore undergoes oxidation treatment at a limited temperature range while being suspended by excess air or oxygen combustion gases in the pre-reduction furnace exhaust gas.The oxidized ore is fed from the transfer line 17 to the pre-reduction furnace 10. Ru.

As mentioned above, a multistage suspension preheater has better thermal efficiency, but a single stage type is also possible.

Examples of the present invention are shown below.

1) Chromium ore Wamu E stone composition from the Philippines 0r2
03; Q de, -%, Fed: Ko J, t% particle size M
~Ill mesh: 7, 9%, 1it-10
0rnos'nr g4.7%, ]1/θOm@sh or less: yo, da arc 2) Oxidation treatment furnace operation data Furnace type 1 Fluidized bed chromium 1 stone supply amount s /? jbB/hr Amount of exhaust gas blown from the preliminary reduction furnace: 410 Nm3/hr Air amount: Rich! rM! I13//hr Furnace temperature: 1ooo℃ 3) Pre-reduction furnace operation data Furnace type: Supply amount of fluidized bed oxidized chromium ore: / ? ! J9/
hr Coke oven gas supply amount g/JOM'/ hr Furnace temperature: 1 oso℃ Pre-reduction s: y% In order to compare the preliminary reduction effect of the above example, oxidation treatment is not performed on the above example When preliminary reduction was performed under the same operating conditions as HakaT, the return rate was 416%.
It declined to .

As explained above, if the method of the present invention is carried out using the apparatus of the present invention, the reduction rate can be improved in the preliminary reduction method as a preliminary step of the smelting reduction method of chromium ore, which is difficult to reduce. It is possible to increase the temperature of the chromium ore fed to the pre-reduction furnace.

The effects of the method and apparatus of the present invention are summarized as follows.

1) By oxidizing chromium ore, its reduction efficiency can be increased in a preliminary reduction furnace.

2) Since the chromium ore is heated in the oxidation treatment furnace and charged directly into the pre-reduction furnace, the amount of heat required in the pre-reduction furnace can be reduced.

3) Exhaust gas from a preliminary reduction furnace or a smelting reduction furnace can be used as the processing gas for the oxidation treatment furnace.

4) When using 7 lux such as limestone, if CaO is generated from it in advance in an oxidation treatment furnace, the amount of heat consumed in the 1,000m reduction furnace can be reduced.

[Brief explanation of drawings]

Figure 1 is a chart showing the relationship between warm oxidation treatment and Cr2O3 peak intensity in X-ray diffraction performed on oxidized chromium ore. Figure 3 is a diagram showing the relationship between the reduction rate of chromium ore and the reduction rate of chromium ore.
- Sheet, Figure D is the 70-sheet of another preliminary reduction device. l... Oxidation treatment furnace, 3... Chromium ore supply port, D... Oxidation treated ore transfer pipe,! ,! '+1・
- Air or oxygen supply port, 6... Pre-reduction exhaust gas conduit, 10... Pre-reduction furnace, /c... Reducing gas supply port, /U - Pre-reduced ore discharge port, lj *
/J'...Exhaust port for preliminary reduction waste, ldar/da'*
/4t'...Susvenge adventure preheater, lj.
... Crumb ore supply pipe, 16... Air or oxygen supply pipe, /7-- Oxidized ore transfer pipe. Patent applicant Kawasaki Steel Co., Ltd. Representative Patent Attorney Mura 1) Politics JII Diagram 0 500 700 900 1100 1300 Meeting L4 Hiss! 5X friend (0C) Fulter Fe Crz03 edit (L, +, Q) = (o+2)
Person, 86--14 seven-year-old labor purchase-4 屓 (・C)

Claims (1)

[Claims] 1. A method for melting and reducing chromium ore using a pre-reduction furnace and a smelting reduction furnace.
A method for pre-reducing Rishimu ore, which comprises oxidizing it with air or oxygen at a temperature of 00 to 1300°C, and then supplying the oxidized Simu ore to a pre-reduction furnace for preliminary reduction. 2. A vertical oxidation treatment furnace is installed above the main furnace, and the oxidation treatment furnace has a chrome ore supply port, an air or oxygen supply port, and a preliminary reduction furnace exhaust gas supply port , a transfer pipe for the oxidized chromium ore, a discharge port for the exhaust gas from the oxidation treatment, a 7-lux supply port and a reducing gas supply port as necessary, and the pre-reduction furnace is provided with a reducing gas supply port. A supply port, a discharge port for pre-reduced exhaust gas, and a discharge port for pre-reduced chromium ore are provided, and the fermentation treatment furnace and the pre-reduction furnace are connected by a transfer pipe for the chromium ore and a conduit for the pre-reduction furnace exhaust gas. A preliminary reduction device for chromium ore, which is characterized by: S. The chromium ore preliminary reduction apparatus according to claim 2, wherein the treatment furnace is a fluidized bed reactor. Number! 3. The chromium ore preliminary reduction apparatus according to claim 2, wherein the I-forming treatment furnace is a suspension preheater.