JPS58100640A - Preliminary reducing method for chromium ore - Google Patents

Abstract

PURPOSE:To perform low temp. preliminary reduction of chromium ore, by supplying coke furnace gas into a preliminary reducing furnace at prescribed ratios with respect to the introducing rate of the waste gas of a melting and reducing furnace and the amt. of the chromium ore to be supplied and further supplying carbonaceous materials in such a way as to exist in a specified amt. CONSTITUTION:Coke furnace gas as the methane source is supplied together with the waste gas produced from a melting and reducing furnace of the next stage into a preliminary reducing furnace in the range of 10-70% introducing rate of the above-described waste gas and 400-1,200Nm<3>/t-ore based on the amt. of the chromium ore to be supplied. Further, carbonaceous materials (e.g.; coke) are supplied into the fluidized layers of the preliminary reducing furnace so as to maintain 10-60% ratio based on the amt. of the ore. When the reducing temp. cannot be maintained only by the sensible heat of the waste gas of the melting and reducing furnace, the combustion heat of the carbonaceous materials is utilized by blowing O2 and high temp. air. This preliminary reducing temp. is maintained at 900-1,100 deg.C and the preliminarily reduced ore contg. the carbonaceous materials is discharged and is fed to the melting and reducing furnace of the next stage, where ferrochromium is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a flow prereduction process K11 of chromium ore for the production of ferrochrome.

Chromium ore resources are trending toward lower grade and fine mineralization. Ferrochrome is usually produced by smelting chromium ore using an electric furnace, but the electric power consumption reaches several thousand xwn/lK, 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 electricity. 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. Of course, it can also be applied to the production of ferrochrome from chromium ore.

However, when high-temperature exhaust gas from a smelting reduction furnace is used as a reducing gas in a pre-reduction furnace for hard-to-reducible ores such as chromium ore, chromium oxide (CrtOs) and iron oxide contained in PM ore are used. Since it is difficult to reduce compared to (Fed), there is a problem that the preliminary reduction rate of the chromium ore as a whole does not increase.

The present inventors have also proposed a method using a reducing agent such as heavy oil or coal as a preliminary reduction method for chromium ore, but it is necessary to maintain the temperature inside the reactor at 1100 to 1300"C. , is not suitable when the exhaust gas temperature from the smelting reduction furnace is low.

It is known in the literature that methane (CH4) is effective as a reducing agent when reducing chromium ore at low temperatures. Using liquefied natural gas (LNG) as methane is expensive and impractical. The present inventors have focused on coke oven gas as a source of methane that can be easily used in steel plants.

However, in a reduction experiment of chromium ore using a fluidized bed reduction apparatus using coke oven gas, as shown in the human curve in Figure 1, the reduction rate hardly increased below 1000°C, and above 1000°C. In this case, the chromium ore particles stick to each other and cannot maintain a fluidized state.

The composition of coke oven gas is as shown below.
Also contains Hn + Cot and H, O.

C-H 420-26% H, 57-65% CO5-891+ Co, 1-3% N, 2-4- CmHn 2-3% H, 02-3- Therefore, the coke oven gas is different from the case where only methane is used. have different reduction behavior. Further, coke oven gas is not used alone in the pre-reduction furnace, and consideration must be given to mixing it with high-temperature exhaust gas from the smelting reduction furnace.

In view of the above-mentioned circumstances, the present inventors conducted various experiments to discover a method for preliminary reduction operation of low-temperature chromium ore using coke oven gas, and as a result, they arrived at the present invention.

The gist of the present invention is to use a device consisting of a pre-reduction furnace and a smelting reduction furnace to introduce the smelting reduction furnace exhaust gas into the pre-reduction furnace to pre-reduce the granular ore through fluidization, and then supply it to the smelting reduction furnace and melt it. In the preliminary reduction method of chromium ore for producing metal, coke oven gas is introduced into the preliminary reduction furnace, the amount of smelting reduction furnace exhaust gas introduced is 010 to 70 cm, and the amount of chromium ore supplied to the preliminary reduction furnace is 400 to 120 ON/7//. The amount of carbon material is supplied within the range of one ore, and the amount of carbon material in the fluidized bed of the main furnace is maintained at 10 to 60 inches relative to the amount of ore, and oxygen or air is supplied as necessary. The present invention relates to a method for pre-reducing chromium ore, which is characterized in that the pre-reduction temperature of chromium ore is maintained at 900 to 1100° C., and the pre-reduced ore mixed with carbonaceous material is discharged.

Since CO1, H, and O contained in coke oven gas inhibit the reduction reaction, it is effective to add carbonaceous materials such as coke and coal to chromium ore in order to deal with this. As is well known, at reduction temperatures below 1100'C, the rate of reduction by carbonaceous materials such as coke and coal is low. However, CO in carbonaceous materials and coke oven gas,
and H20 cause a trusion loss reaction and produce CO and Hl.
As a result, the reduction reaction is promoted by converting K into K. Furthermore, by adding carbonaceous material to chromium ore, it is possible to prevent fluidization inhibition due to mutual adhesion of chromium ore particles even if the reduction temperature is increased to 1000°C or higher. teeth,
The relationship between temperature and reduction rate is shown when a charge of chromium ore 85-1 carbon material 15- is reduced with 30 liters of coke oven gas and reducing gas 70-, and fluidization inhibition can be prevented. It was possible to raise the reduction temperature and increase the reduction rate.

The mixing ratio of carbonaceous material mixed into chromium ore is such that if the carbonaceous material is less than 10% of the chromium ore, there is little effect in preventing fluidization inhibition due to mutual adhesion (sintering phenomenon) of chromium ore particles; However, since the volume is too large and the productivity per reaction volume decreases, 10 to 60 inches is appropriate.

If the particle size of the carbonaceous material to be mixed is too different from the particle size of the chromium ore, segregation will occur, so it is desirable that the particle size is about the same. The particle size Fi of the chromium ore used in the experiment was 48 to 100 mesh and 80 or more, whereas the particle size of the carbon material mixed therein was 48 to 100 mesh.

Next, we investigated the relationship between the reduction rate by changing the ratio of coke oven gas and other reducing gases such as CO and H3, and examined the results in the second section.
As shown in the figure. Curve C in Figure 2 is the reduction temperature too'c%-
The lines are for a reduction temperature of 1100°C. It is clear from FIG. 2 that the reduction rate can be increased by mixing in coke oven gas. If the mixing ratio of coke oven gas is less than 1 (l), the effect will be small, and if it is too much, the effect will be reduced, so a range of 10 to 70 l is suitable for the reducing gas.

Figure 3 shows the relationship between the amount of coke oven scum and the reduction rate relative to the amount of ore. In the figure, curve E is for the case where the reduction temperature is 1000°C, and curve F is for the case where the reduction temperature is 1100''C.

From Figure 3, the coke oven gas amount is 400 Nvl/-
For more than ore, 600 Nrd/ ore is required, and the reduction rate is highest near one ore, and above that, the reduction rate tends to decrease. Considering the cost, the upper limit is about 1200 Nvl/l-ore.

FIG. 4 is a cross-sectional view schematically showing an embodiment of a fluidized pre-reduction furnace used in carrying out the method of the present invention.

The pre-reduction furnace 1 consists of a fluidized bed reactor, and is usually vertically cylindrical in shape. Powdered chromium ore is available at chromium ore supply port 3.
The fluidized bed 2 is then supplied to the pre-reduction furnace. The pre-reduced ore which has been pre-reduced in the pre-reduction furnace 1 is discharged from the pre-reduced ore discharge port 4 and is transported and blown into a smelting reduction furnace (not shown). Carbon materials such as coke and coal, flux, etc. may be mixed with chromium ore and may be supplied, or may be supplied from separate supply ports 5, 5.

High temperature exhaust gas from the smelting reduction furnace is supplied from the supply port 8 at the bottom of the fluidized bed. The gas distribution plate 9 can be provided as necessary.

Coke oven gas is supplied from the supply port 6 on the side of the preliminary reduction furnace 1 . It can also be mixed with high-temperature exhaust gas from the smelting reduction furnace and supplied from the exhaust gas supply port 8.

Using fluidized pre-reduction furnace 1, reduce the reduction temperature to 900-110
0°C1 The amount of carbonaceous material supplied is such that the ratio of carbonaceous material and chromium ore in the fluidized bed is maintained at 10 to 60 degrees, and the amount of coke oven gas supplied is 400 to 120 degrees of chromium ore.
By carrying out preliminary reduction of chromium ore under operating conditions of NtIl and smelting reduction furnace exhaust gas amount of 10 to 70 degrees, a preliminary reduction rate of chromium ore of 20 to 60 degrees can be achieved.

If the necessary reduction temperature of 900 to 1100'C cannot be maintained with only the sensible heat of the exhaust gas from the smelting reduction furnace, it is necessary to preheat the chromium ore by heat exchange with the exhaust gas discharged from the outlet 10 of the preliminary reduction furnace. I'll go. As a method for preheating chromium ore, a method using a multi-stage fluidized bed or a method using a suspension preheater e is suitable.

If the amount of heat is insufficient due to the sensible heat of the high-temperature exhaust gas from the smelting reduction furnace and the preheating of the charged ore, oxygen or high-temperature air is supplied from the supply lower to partially burn the carbonaceous material to CO. Heat can be used.

Powdered carbonaceous material mixed in the pre-reduced ore discharged from the pre-reduced ore discharge port 4 is blown into the smelting reduction furnace together with the pre-reduced ore and is consumed as a reducing agent and fuel. Therefore, the amount of coke charged into the smelting reduction furnace is reduced,
This has the great advantage of saving lump coke.

According to the method of the present invention, as with the use of coke oven gas and carbonaceous material, chromium ore, which conventionally has been difficult to reduce with only exhaust gas from a smelting reduction furnace, can be pre-reduced at a relatively low temperature.

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

(1) $1 Coke oven gas, which is easily available in ironworks, can be used as a methane source.

(2) By mixing carbonaceous material into chromium ore, the reducing power of coke oven gas can be increased.

(3) By adding carbonaceous material, it is possible to prevent the chromium ore particles from sticking, thereby increasing the reduction temperature and increasing the preliminary reduction rate.

(4) When the reduction temperature cannot be maintained by the sensible heat of the smelting reduction furnace exhaust gas alone, the combustion heat of the carbonaceous material can be utilized by blowing in oxygen or high-temperature air.

(5) Since the carbonaceous material is blown into the smelting reduction furnace together with the preliminary reduced ore, the amount of coke consumed in the smelting reduction furnace can be reduced. That is, lump coke can be replaced with powdered carbonaceous material.

Next, examples of the present invention will be shown below.

Example 1) Chromium ore: Chromium ore from the Philippines Composition: C
rto, 49.25k Fe0 23.8- Grain 11: 28-48M 7.9 Arrogant 48-100M
86.7mm 100M or less 5.4mm (M is mesh) 2) Charcoal material: Coke (CDQ (coke dry quencher) dust) Particle size: 48-100 mesh 3) Pre-reduction furnace operation data Chrome ore Supply amount: 175 Nm'/hr Charcoal material supply amount = 68 Mutsumi/hr (Charcoal material/Chromium ore = 39 Chi) Melting reduction furnace exhaust gas amount: 590 Nm'/ hr Coke oven gas amount: 12 ON7F// hr (Coke oven Gas amount / smelting reduction furnace exhaust gas amount = 20%) (Coke oven gas amount / chromium ore amount = 686 Nm / one ore) Oxygen amount: 47 Ni/hr Pre-reduction furnace temperature: 1030℃ Pre-reduction rate of chromium ore: 38 chi

[Brief explanation of the drawing]

Figures 1 to 3 show the reduction temperature, coke oven gas concentration, and amount of coke oven gas relative to the amount of ore, respectively. A chart showing the relationship between K and the chromium ore preliminary reduction rate, and FIG. 4 is a schematic longitudinal sectional view of the preliminary reduction furnace. Mu... 100% chromium ore charged coke oven gas 10
In the case of 0S, B... 85% chromium ore, 15% carbonaceous material, 30% coke oven gas, 70% reducing gas, C, E
...When the reduction temperature is 1000°C, D. F... When the reduction temperature is 1100°C, 1... Pre-reduction furnace, 2... Fluidized bed, 3... Chromium ore supply port, 4
...Preliminary reduced ore discharge port, 5...Charcoal material and flux supply port, 6-...Coke oven gas supply port, 7...Oxygen or high temperature air supply port, 8...Melting reduction furnace Exhaust gas supply port, 9...gas distribution plate. Figure 1 Dogenshin Cliff ('C) Figure 2

Claims (1)

[Claims] 1 Preparation of chromium ore using a device consisting of a pre-reduction furnace and a smelting-reduction furnace, introducing the smelting-reduction furnace exhaust gas into the pre-reduction furnace, fluidizing the granular ore and supplying it to the smelting-reduction furnace to produce molten metal. In the reduction method, the amount of coke oven gas introduced into the preliminary reduction furnace is 10 to 70-
400 to 120 per amount of chromium ore supplied to one preliminary reduction furnace
ONm'/ is supplied in the range of one ore, Km material is supplied so that the amount of carbon material in the fluidized bed of the pre-reduction furnace is maintained at 10 to 60 - relative to the amount of ore, and oxygen is added as necessary. Or supply air and adjust the pre-reduction temperature to 900-1100°.
A method for pre-reducing chromium ore, which is characterized by discharging pre-reduced ore mixed with carbonaceous material.