AU644651B2 - Method for producing alloying components - Google Patents

Description

64465 41

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: ::96.

Priority: Related Art: see TO B Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: E COMPLETED BY APPLICANT OUTOKUMPU OY LANSITUULENTIE 7 A 02100 ESPOO

FINLAND

GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

complete Specification for the invention entitled: METHOD FOR PRODUCING ALLOYING COMPONENTS.

The following statement is a full description of this invention including the best method of performing it known to me:- METHOD FOR PRODUCING ALLOYING COMPONENTS The present invention relates to a method for producing alloying components using sulphidic raw materials and relates particularly, but not exclusively, to producing nickel raw material.

While producing stainless steels, the employed alloying components are, among others, chromium and nickel.

Chromium is advantageously alloyed in steel by employing ferrochromium as the starting material in the production, because the proportion of chromium in stainless steel is generally higher than that of nickel. Nickel is usually ,upplied in connection with the converting treatment of steel, for example as metallic, oxidic or ferronickel. The nickel oxide used as an alloying component, as well as the ferronickel, are produced with oxidic starting materials.

Metallic nickel, on the other hand, is generally produced with sulphidic starting materials. The raw material differences in the products are mainly due to the other components contained in the raw materials, and the benefit gained by them determines the advantageous method for production. Moreover, the impurities contained in the raw materials, such as copper, are important for achieving an advantageous production process.

25 The use of sulphidic materials in the production of ferronickel, used as an alloying component, has earlier been prevented by the problems caused by the removal of *9 sulphur and for iLntance copper in the production of steel.

It is an object of the present invention to 30 attempt to overcome one or more of the aforementioned problems.

According to the present invention there is Sprovided a method for producing alloying components, from sulphidic raw materials, comprising: a) roasting the sulphidic raw material in order to transform iron and nickel contained therein to an oxidic form to thereby form an intermediate raw material product; b) subjecting the intermediate product obtained from roasting in step to pelletising and sintering to process the intermediate product to pellets of an advantageous particle size for alloying processing.

Preferably, the raw material of a sulphidic alloying component is first dead roasted in order to remove, for the major part, the sulphur contained in the raw material, and in order to transform the other main components contained in the raw material, i.e. iron and nickel, to an oxidic form. When it is desired to produce ferronickel ie an iron containing nickel, the intermediate product obtained from roasting, i.e. the calcinate, is subjected to sintering in order to achieve a pellet size suitable for further treatment. The pellets obtained from sintering can be directly fed into the production of steel, if the alloying component nickel is wished to be fed into further treatment in oxidic form.

The pellets obtained from sintering can also be melted, in e reducing conditions, in order to create a ferronickel product. The ferronickel obtained from the smelting furnace is advantageously for instance granulated.

S Although an essential amount of the sulphur content of the raw material is removed in connection with roasting, there may still renain some sulphur in the granulated product and this is mainly based on the carbon used as a reductant and 30 which can, if necessary, be removed for example by a lime and/or calcium carbide treatment.

Thus, a sulphidic material can be used as the raw material in the production of ferronickel. In a preferred method the first stage, i.e. the roasting of the sulphidic iron-nickel concentrate, is advantageously carried out at a temperature of substantially 950 0 C, so that the amount of sulphur contained in the intermediate product obtained from roasting is advantageously below 1% by weight. The sulphur dioxide gases created in the roasting are conducted to further treatment, for instance to the production of sulphuric acid. Iron and nickel are present mainly in oxidic form in the calcinate.

From the calcinate obtained for the production of ferronickel, the calcinate is first pelleted, if necessary, by grinding to a desired size, and then the pellets are sintered. The sintered iron-nickel pellets are thereafter conducted to a smelting furnace, which is advantageously for instance an arc furnace, where the pellets are smelted in reducing conditions by means of carbon or coke. The carbon monoxide gas obtained from the smelting furnace can advantageously be recirculated in the sintering stage of the pellets, in order to create advantageous conditions for the sintering.

The smelting product obtained from the smelting furnace can be granulated for further treatment of the product, or the smelting product can be directly transported, in molten state, to the production of steel.

dependent on the sulphur content of the product. If the sulphur content surpasses a predetermined limit, the smelting product is subjected to the removal of sulphur, for example by means of lime treatment, prior to feeding it into the production of steel.

30 In a particular example an iron-nickel sulphide concentrate, containing 20% by weight nickel, 30.9% by weight iron, 30.1% by weight sulphur, 0.56% by weight cobalt, 6.3% by weight magnesia, and 3.3% by weight silicon C3 oxide, as well as copper and arsenic less than 1,000 ppm, was roasted at the temperature 950 0 C. The sulphur dioxide containing gases created in the roasting at the rate 2,000 Nm 3 were conducted to heat recovery and gas cleaning, and to further processing for instance in the production of sulphuric acid. The calcinate, on the other hand, was conducted to a sintering plant to be first pelleted. The employea pelleting binder was bentonite. The pelleted calcinate was sintered by using carbon monoxide and carbon, at the temperature 1,300 1,350 0 C, in a band sintering machine, whereto the calcinate to be sintered was fed at one end and discharged at the other. The flue gases from the sintering were subjected to gas cleaning for instance in order to remove sulphur.

The sintered pellets, together with flux, sand and burnt lime, were further conducted, via a preheating treatment, to an arc furnace to be smelted. The smelting in the arc furnace took place in reducing conditions, where the employed reducing agent was coke. The slag now 20 obtained from the arc furnace contained 45% by weight silica, 29% by weight magnesia, 11% by weight calcium oxide, and 5% by weight aluminium oxide. The ferronickel obtained from the arc furnace contained 37% by weight nickel, 57% by weight iron, 1.0% by weight silicon and 25 by weight carbon, and also a slight amount of sulphur. The flue gases from the arc furnace were first subjected to the removal of solid particles, whereafter part of the carbon monoxide containing gases were circulated back to the sintering of pellets. The rest of the flue gases goes to further cleaning, and thereafter advantageously to the production of energy.

In order to clean the ferronickel obtained from the arc furnace of the remaining sulphur, the ferronickel S was subjected to a sulphur-removing treatment prior to transporting it to be used as a raw material in a steel plant.

0*.0 6 S 6.

Claims (8)

1. A method for producing alloying components, from sulphidic raw materials, comprising: a) roasting the sulphidic raw material in order to transform iron and nickel contained therein to an oxidic form to thereby form an intermediate raw material product; b) subjecting the intermediate product obtained from roasting in step to pelletising and sintering to process the intermediate product to pellets of an advantageous particle size for alloying processing.

2. The method of claim 1, comprising smelting the pellets prior to using the nickel contained in the raw material as an alloying component.

3. The method of claim 1 or 2, comprising processing at step so that the nickel is converted to ferronickel.

4. The method of any one of claims 1, 2 or 3, wherein step is carried out at a temperature of substantially 950 0 C.

5. The method of any one of the preceding claims wherein t-e sintering takes place within the temperature range 1,300 1,350 0 C.

6. The method of any one of claims 1, 4 or S. comprising processing at step so that the nickel is 25 converted to nickel oxide.

7. An alloying component produced by the method of any one of the preceding claims. S9

8. A method substantially as herein described with reference to any one of the examples. DATED THIS 15TH DAY OF OCTOBER 1993 OUTOKUMPU OY By Its Patent Attorneys: GRIFFITH HACK CO Fellows Institute of Patent SAttorneys of Australia (57) ABSTRACT The invention relates to a method for producing alloying components, particularly in the case of producing a nickel raw material to be used as an alloying component, of a sulphidic raw material. According to the invention, the sulphidic raw material is first roasted in order to trans- form the iron and nickel contained therein essentially com- pletely into oxidic form. Thereafter the intermediate product obtained from roasting is subjected to pelleting and sintering in order to process the intermediate product into particle form. I 1o 0 *go 4* N *p