JPS58174528A - Manufacture of chromium-contg. reductively sintered pellet - Google Patents

Abstract

PURPOSE:To inhibit the reduction of formed pellets in strength, by acid-pickling chromium-contg. dust formed from the process of manufacturing ferrochromium, adding it to the raw material of a chromium ore, and then forming the mixture into pellets. CONSTITUTION:Chromium-contg. dust formed from the process of manufacturing ferrochromium, e.g. reductively roasting a chromium ore, is treated with an aqueous acid solution such as hydrochloric or sulfuric acid. The treated dust is reused by adding it to a raw material for the reductively roasted pellets of the chromium ore. The pellets obtained in this way do not reduce strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing reduced sintered pellets of chromium ore.

When producing ferrochrome, the method used is to pre-reduce raw material chromium ore with carbon to produce sintered pellets, and then smelt the pellets in an electric furnace to produce ferrochrome.

These reduced sintered pellets are obtained by mixing chromium ore powder and carbon powder, granulating the mixture, and roasting the mixture in a rotary kiln or the like.

Dust containing chromium is generated from this roasting process and the subsequent smelting process using an electric furnace. In addition, the manufacturing process of low carbon ferrochrome, that is, melting chromium ore and quicklime in an electric furnace,
It is also used in an electric furnace when silicochrome is added to make low-carbon ferrochrome, but since it also contains a considerable amount of chromium, it is imperative to make effective use of it. In particular, the dust generated from the roasting process of reduced sintered pellets has a high chromium content, and is preferably reused as a raw material for ferrochrome.

For this reason, it has been proposed to use the dust generated from the roasting process of reduced sintered pellets by returning them to the raw material for the pellets. However, the strength of pellets to which dust has been added decreases, causing problems such as pellet destruction and dam ring adhesion within the rotary kiln for reduction roasting.

Possible countermeasures for this are: a) increasing the amount of binder for granulation to make the pellets stronger; b) reducing the amount of reducing carbon material to make the pellets stronger; No. 9 Fine powder for granulation There are methods such as pulverizing the pellets and strengthening the pellets. However, in (a), the cost for the binder increases;
), the reduction rate decreases due to the decrease in reducing agent. However, there are problems such as an increase in the cost of power for crushing.

The present invention is based on the discovery that if dust is treated with an acid aqueous solution and the treated dust is added to the raw material for pellets, the strength of the pellets does not decrease.

That is, the present invention treats the dust generated from the ferrochrome manufacturing process such as the reduction roasting process of chromium ore with an acid aqueous solution such as hydrochloric acid or sulfuric acid, and adds the treated dust to the raw material for reduction roasting pellets of chromium ore. This method is characterized by the fact that it is reused.

In addition to the dust generated from the above-mentioned reduction and roasting process of chromium ore, the dust generated from the ferrochrome smelting electric furnace, the electric furnace for melting chromium ore and quicklime, and the ferrochrome manufacturing process. can be used.

An example of dust is the reduction roasting process (rotary kiln)
The analytical values for what is generated are shown below.

(1 child %) An example of dust pickling solution treatment is a stirrer.
Put the dust into a treatment tank with a temperature of 100 ml, add an aqueous acid solution, and stir. Let the dust-suspended liquid overflow,
This is transferred to a settling tank, the settled slurry is extracted from the bottom, and the supernatant liquid is treated separately as wastewater.The slurry is then transferred to a filter and separated into water and slurry.This slurry is It is dehydrated, dried if necessary, and added to the raw material for pellet granulation as a chromium source.

As the acid aqueous solution used above, mineral acids such as hydrochloric acid and sulfuric acid are suitable, and the daughterness is not particularly limited, and is PH□.

Dilute acid water of about 6 or less: 1i solution is sufficient. The treatment tank does not need to be particularly heated and may be kept at room temperature.

It is not clear why the strength of the pellets during the roasting process decreases when dust is added to the pellet raw material, but as mentioned above, dust contains a large amount of Zn in the form of metal or its compounds. It is possible that there is a shadow of this.

In addition, dust contains higher concentrations of alkali metal compounds and alkaline earth metal compounds than those found in chromium ore, and it is assumed that these also have some effect.

Therefore, according to the present invention, these components are removed from the dust by pickling the dust, so it is presumed that a decrease in the strength of the pellets can be avoided.

Experimental example capacity 2rr? Dust to the treatment tank at 0.2 Vb, water at 5
Hydrochloric acid is supplied at a rate of s/h so that the pH of the liquid in the treatment tank becomes approximately 18, and the overflow water is led to a settling tank, and the slurry that has settled at the bottom is periodically drained into the slurry tank. , the slurry is pumped to a filter, filtered and
Washing with water gave a residue. After drying this residue, it was added twice to a mixture of chromium ore powder and carbon powder, which are raw materials for pellet production, and granulated. (Size, diameter: approximately 15 mm) The granulated pellets were dried at 120°C for 2 hours, heated at a heating rate of 10°C/min in a chemical atmosphere, and held at the temperatures shown in Table 2 for 5 minutes each. After that, it was slowly cooled. Next, the strength of this pellet was measured using a Honya type crushing strength measuring device.

Similarly, pellets with untreated dust added and with no dust added at full heat were also tested. These results are summarized in Table 2.

As can be seen from the table, although it is not related to the type of acid used, it is desirable that the pH in the treatment tank is 6 or less.

Table 2 The analysis values of dust (dry) after treatment of Table Nakabana 3 are as follows. ,,:,:.

0r203 FeOOZn Alkaline content Alkaline earth 16.8% 12.4 34.2
0.7 0.1 4.0 Furthermore, as a result of roasting the pellets produced by the method of the present invention in an actual rotary kiln, hardly any destruction of the pellets or adhesion of dam rings was observed.

Applicant: Showa Denko Co., Ltd. Shunan Denko Co., Ltd. Agent Chrysanthemum Earth Spirit - □

Claims (1)

[Claims] A method for producing reduced sintered pellets of chromium ore, in which chromium-containing dust generated from the ferrochrome production process is fermented and added to the raw material.