JPS5822355A - Preparation of ferrochrome by rotary furnace - Google Patents

Abstract

PURPOSE:To prepare ferrochrome without using an electric furnace using expensive electric power, by a method wherein chromium ore, a slag forming agent and a carbonaceous reducing agent of which the layer thickness is held to a specific thickness or more into a rotary furnace and the carbonaceous reducing agent is burnt by blowing oxygen to melt and reduce said ore. CONSTITUTION:As a rotary furnace, a horizontal type one or an inclined type one having an opening at both ends thereof or at one end thereof is used. Into this rotary furnace, chromium ore in a powder form, a lump form or a pellet. briquet form, a slag forming agent such as silicon or lime and a carbonaceous reducing agent such as coke or coal are charged. In this condition, oxygen is blown thereinto from an oxygen blowing lance to burn the carbonaceous reducing agent and said ore is melted and reduced to prepare ferrochrome. Over 70% or more during this total blowing time or at least over 15min or more directly before blowing is completed, the layer thickness of the carbonaceous reducing agent is held to 50mm. or more to increase a Cr reducing ratio (a Cr recovery ratio).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ferrochrome using a rotary furnace. This relates to a method for producing ferrochrome by burning a carbonaceous reducing agent in coal fat with oxygen and using the combustion heat to reduce chromium ore fed into the same rotary furnace.

Conventionally, to produce ferrochrome, chromium ore, a slag-forming agent, and a coke cape reducing agent are continuously charged into a submerged arc electric furnace and smelted. With this method, 1 ton of ferrochrome can be used for power-consuming industries.3. ooo~to7
0 OK, W, H are required, and it can be said that it is a typical power-consuming industry. These days, when energy-saving technology is being called for, the efficiency of converting valuable liquid fuel into electrical energy is extremely low, so the development of technology that avoids the use of large amounts of electricity is an urgent and important issue.

On the other hand, regarding iron smelting using rotary furnaces,
045), and regarding iron alloy smelting,
There is a proposal for No. 4-25751. However, in these proposed smelting methods, coal, coke, and graphite are used as reducing agents, and the layer thickness of the reducing agent on the slag surface is limited to 50 to 50 cm, resulting in a weak reducing atmosphere and poor product quality. The holder is bad. For example, when manufacturing ferrochrome, the Cr yield is about 75%.

Furthermore, in each of the above proposals, the oxygen blowing lance is oriented upward or horizontally, and combustion occurs near the refractory, increasing the proportion of radiant heat and conductive heat from the refractory. As a result, not only is the thermal efficiency extremely low, but also in smelting where it is necessary to maintain slag at a constant slag temperature, refractories are exposed to extremely high temperatures and are subject to significant wear and tear. Furthermore, fine metal particles adhere to the surface of the discharged reducing agent, but this is not reused, which is one of the reasons for the low product quality*b mentioned above. There's a problem.

The present invention addresses the above-mentioned problems and provides a method for producing ferrochrome as an alternative to the conventional electric furnace smelting process. It was invented by.

That is, the gist of the present invention is to feed chromium ore, a slag-forming agent, and a carbonaceous reducing agent into a rotary furnace, and blow oxygen into the furnace to burn the carbonaceous reducing agent and melt and reduce it. This is a method for producing ferrochrome using a rotary furnace, in which the layer thickness of the carbonaceous reducing agent is maintained at 50 cm or more.

However, it is essential to keep the thickness of the carbonaceous reducing agent layer at 50 or more for at least 70 or more of the total blowing time, or at least 15 minutes or more before the end of blowing. It is necessary to enhance the effectiveness of the invention.

Furthermore, it is necessary to recirculate the carbonaceous reducing agent by attaching a skinmer to the sprue of the rotary furnace in order to enhance the effects of the present invention.

Furthermore, an oxygen tempering lance is attached to the rotary furnace in a downward direction, and oxygen is blown into the rotary furnace to burn the carbonaceous reducing agent.
Applying this combustion heat directly to the hot water surface is necessary to enhance the effects of the present invention.

Next, a method for producing ferrochrome using a rotary furnace according to the present invention will be explained in detail.

The rotary furnace used in the production method of the present invention is generally a horizontal type with a single opening or an inclined type II (inclination angle #irm x 55°
(preferably) rotary furnace. As a result of research conducted by the inventors, it has been confirmed that it is preferable to charge the preheated or prereduced raw material chromium ore and the slag forming agent together with the carbonaceous reducing agent. Next, the chromium ore used in the present invention is fine ore, lump ore, pellets/platen) (m
It may be either the heat or unfired bottom side, or it may have a charcoal interior. Silicone and lime leather commonly used by Slag Makers may be used. The carbonaceous reducing agent may be coke, coal, a mixture thereof, pulverized coal or pulverized coal water slurry, for example, as disclosed in Japanese Patent Application No. 56-4614 by the group of the inventors.
No. 9, Japanese Patent Application No. 1984-46150, Special Application No. 1983, +
It is preferable to use it together with the coal emulsion proposed in No. 46151 in terms of energy conservation and resource conservation. Figure 1 is a graph showing the relationship between the zero snow blowing rate on the surface of Hiro coke and the amount of refractory loss, and Figure 2 is the relationship between the layer thickness of the reducing agent and the Cr reduction rate (metal recovery rate). Fig. 5 is a graph showing the relationship between the recycling rate of excess coke and the metal recovery rate. As shown in Figure 2, it can be seen that the reduction agent layer thickness is required to be at least 5 m (1 m or more) in order to reduce the amount of wear on the refractory and to achieve a high Cr reduction rate (metal recovery rate). It can be seen that a layer thickness of 50 mm or more is preferable in terms of the circulation of excess coke and the high metal recovery rate.Furthermore, as shown in Figure 1, the oxygen blowing lance is installed downward, and from now on. It can be seen that if oxygen is blown in to combust the carbonaceous reducing agent and the combustion heat is directly applied to the hot water surface, the amount of loss of refractories can be extremely reduced.

In this way, thermal efficiency can be improved by directing the oxygen blowing lance downward and increasing the proportion of combustion heat that burns the reducing agent on the slag surface and directly transfers to the slag. Also,
The refractory surface temperature varies depending on the oxygen flow rate toward the reducing agent, so if blowing is performed using a downward-facing two-pronged lance so that the total oxygen blowing amount of 40 to 909 I is directed downward, the refractory surface temperature can be adjusted. The slag temperature was increased to 175 without increasing the temperature.
It is possible to maintain the temperature around 0°C. Since the refractory surface 4 is not subjected to high-temperature heating, the amount of wear and tear is reduced.

Also, when the oxygen blowing lance is facing downward, if the reducing agent layer is thin, it will create a weak reducing atmosphere.#! This is the range in which the amount of refractory loss can be minimized as the product yield decreases! A metal recovery rate of 86 or more is possible by setting the thickness of the reducing agent layer to 50 or more in I (40 to 90 of the total oxygen amount is downward).

Furthermore, a large amount of reducing agent remains in the furnace at the end of smelting, and a large amount of fine particulate metal adheres to the surface of the reducing agent.

Therefore, if a skinmer is provided at the sprue during tapping and an excess reducing agent of 80 or more is used, the metal recovery rate will be approximately 6.
It was ii+g that it improved and became 929.

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

1! Example-1 Book 1i! An example is an example of high carbon Ferroc DJ-manufacturing.
It was manufactured as follows.

The rotary furnace used was made by the rotary furnace company, with an inner diameter of α42mm, an outer diameter of α76mm, and a length of 1.4s, lined with maguro bricks, tilted 20 degrees with respect to the horizontal direction of the furnace body, and rotated at 8 rpm. . One side of the furnace body has a raw material charging port and a water-cooled lance for oxygen injection.

Raw materials, 72 coke and coke were mixed in the following proportions and charged into the furnace. 5 to 15% of each raw material size was used.

Cr ore: 5011. @Lime18k, :y-/x:
Oxygen was blown into the furnace from a water-cooled lance set on the rotating shaft of the 204 furnace body, and the raw material was melted and reduced by the combustion heat of the coke. The amount of oxygen blown is 1.41JWI/
Start with win, 2.・1.1 NII after 0 minutes //w
in, 55 minutes later α8 Ndl win, 50
After 1 minute, α6Nd was adjusted to 1 m%n.

In addition, additional coke was continuously charged at a charging rate of 1000 gr/min 20 minutes after the start of oxygen blowing, and the coke and bed layer thickness were maintained at about 10.

The hot water was turned on 70 minutes after oxygen injection started. At the time of tapping, a skinmer with a spacing of 5ex from the rice lag was provided at the sprue to tap out the slag and metal, and excess coke and a portion of the slag remained in the furnace and were recycled.

From the next time onwards, the initial coke amount was set to 10 Icf, and the same operation was performed 10 times in succession. As a result, metal and slag with the following weight and composition are obtained, and the metal recovery rate is 9.
It was 2%.

FIG. 4 is a graph showing the relationship between blowing time and manufacturing conditions in Example 10.

11LIF12 books 1N! A complete example is 1911 manufactured using high carbon ferrochrome as follows.

Using the same apparatus as in Example 1, pre-reduced reduced Cr
Pellet ore, burnt lime, and coke were mixed in the following proportions and charged into a furnace.

・Reduced pellet ore: 504. Burnt lime: 5.84. Coke: 204 Chemical composition of reduced beret ore
De&5%810m -15% Mg0, 15% A
Oxygen was blown into the furnace from a water-cooled lance set on the rotating shaft of the ll0I furnace body to melt and reduce the raw materials. Starting with blown oxygen amount B, 1.4 Nm"/11111, the raw material melted after 20 minutes. The slag temperature reached 1.650 °C. From 20 minutes to 50 minutes, 1.1 NII/11n,
From 50 to 40 minutes old, a 8 Ns//m1m,
I went from 40 minutes to 50 minutes with 06 wing 1n. In addition, the regular price of coke is 1.000 gr/mln from 20 minutes.
Continuous charging at a charging speed of approximately 10
It was maintained at am.

Slag temperature reached 1750℃ 50 minutes after oxygen injection started.
The water reached the bath. The distance between the tap hole and the lining is 5a.
No. 11 syanmer was installed, slag and metal were tapped, and excess coke and a portion of the slag remained in the furnace and were recycled.

The same operation was repeated 10 times, with the amount of coke initially charged from next time onwards being set to 10 or more. As a result, the following weight,
Metal and slag having the same composition were obtained, and the metal recovery rate was 95%.

Average weight of 10 times CrF@C ・Metal IA95Kt 53.5% 56.5
a1 Cr, 0. 5IOI CaOAll01 M
gO-1 24.50- α5% 17.51 29
．． 0 50% 28% above implementation ipH1 and l! As is clear from Example 2, according to the method for producing ferrochrome of the present invention, it is possible to produce ferrochrome using lime, which is stably supplied and relatively inexpensive, without using expensive electricity. Moreover, it was confirmed that the thermal efficiency is high, and the metal recovery rate is also extremely high.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the ratio of the amount of molten metal blown onto the coke surface and the amount of refractory wear Oa when using the production method of the present invention, and Fig. 2 shows the same (reducing agent layer thickness and Cr reduction rate). , is a graph showing the relationship between the metal recovery rate, and Figure 5 is a graph showing the relationship between the circulating m usage rate of excess coke and the metal recovery rate. This is a graph showing the relationship between time and various conditions. Agents Patent Attorneys: Jun Sato, Samuro Kimura, Souji Sasaki (Fig. 2 1%) 2m) Part of the calyx (Fig. 3) Gokus 0/Gekiroku no Riki

Claims (4)

[Claims] (1) When chromium ore, a slag-forming agent, and a carbonaceous reducing agent are fed into a rotary furnace, oxygen is blown into the furnace, and the carbonaceous reducing agent is combusted to melt and reduce. A method for producing ferrochrome using a rotary furnace, in which the layer thickness of a carbonaceous reducing agent is maintained at 50 mm or more. (2) The time for maintaining the layer thickness of the carbonaceous reducing agent at 50 mm or more may be 70% or more of the total blowing time (and 4) The scope of the patent claim is that it is 15 minutes or more before the end of blowing. 1st
A method for producing ferrochrome using a rotary furnace as described in Section 1. (3) A method for producing ferrochrome using a rotary furnace according to claim 1, wherein the carbonaceous reducing agent is recycled (by attaching a skinmer to the sprue of the rotary furnace). (4) The oxygen blowing lance was attached to the above rotary furnace in a downward direction so that the total amount of blown oxygen of 40 to 100 seconds directly burns the carbonaceous reducing agent on the hot water surface and gives this combustion heat directly to the hot water surface. A method for producing ferrochrome using a rotary furnace according to claim 1.