non ferrous melting

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60

METALLURGY

UDK 669.053.4.001

Contribution of FGUP GINTSVETMET Institute intoDevelopment and Integration of Autogenous Smelting

V.M. ParetskyFGUP Institute GINTSVETMET)

The autogenous smelting of sulphide

concentrates, ores, and middlings is still the

main direction for improving the technology

for heavy nonferrous metal production.

However, the unique potential of these

processes has not properly been used at the

smelters around the world. This is explained

by the fact that until recently the problems of

one-stage raw material smelting into “the

white matte” (crude metal) and obtaining the

nonferrous metal waste slag have not been

properly studied.

A large volume of recent researches

conducted by Gintsetmet (among others), as

well as the domestic and foreign practice of

developing autogenous processes, including

conversion, enables to conclude that a

significant scientific and technical progress

has been achieved in this field.

The recent theoretical researches

conducted in CIS have indicated that:

1) In case of any type of autogeneous

smelting sulphides are oxidized only in the

melted condition;

2) The oxides with the minimal valency

are formed during such oxidation;

3) Oxidation is effected through the

oxysulphide formation stage;

4) The melt is metallized during suchoxidation;

5) The electron-ions are exchanged in

the molten pool at a high rate;

6) The component dynamics shall be

analyzed in the slag and matte system

subject to the composition and partial

pressure of gas phase components;

7) The elemental sulphur is assimilated

with slag and matte, especially with the

metallized matte, at a high rate;

8) The temperature when the elementalsulfur begins to interact depends on the

sulfidizing agent lattice energy.

These theoretical points have led to a number

of process-related studies at a new technical

level. Below are the results of these studies

conducted recently for various types of

autogeneous smelting.

Oxygen and Flare Melting of Copper

Concentrates into “White Matte” (Crude Copper)

In case of one-stage white matte (crude

copper) production, it is quite beneficial to do

melting with highly basic slags, especially oxide

melts of СаО–FeO–Fe2O3 — SiO2 system. The

advantage of this system is homogeneity at

melting temperatures of 1,200–1,400° С in the

specific Ca/Fe range under high partial oxygen

pressure which is typical for melting to “the

white matte” (crude copper). Besides, the slag is

easily depleted to the waste condition in terms

of the content of nonferrous metals atconsiderably lower costs. The ferrite calcic or

high calcium slags may be used in the ferrous

industry and as a raw material to produce

cement.

The technology for melting copper sulfide

concentrates into “the white matte” (crude

copper) and producing ferriferous calcic silicate

slags was developed for the oxygen and flare

process (OFP). Due to specifics of this process,

it is most suitable for melting with highly basic

slags.The semi-industrial tests were conducted at

the pilot plant with max. capacity 50 t of the

charge per day to melt copper concentrates of

the following composition, %: 18.5–24.0 Сu,

27-32 Fe, 30–35.5 S, 4–6 SiO2 and 0.5 СаО.

The concentrate is pre-dried to the residual

moisture content of < 1%.

The process was conducted by ramping the

copper content in the matte – from “the white

matte” to the crude copper. The quick lime and

limestone were used as a flux. No meltsponging was observed. The furnace was

NONFERROUS METALLURGY NO. 5, 2012



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METALLURGY

operating in the autogenous mode at the slag

temperature of 1,290– 1,350° С. The

following substances were received as the

result of the tests:

• The matte containing 75–79.5% Сu andcrude copper containing 95% Сu, 2.65% S,

0.07% Fe, and 0.53% O2;

• The slag containing 2–3% Сu;

• The gas containing 45–75% SO2,7–

10% O2, 2–20% СO2 and 15–30% N2.

At a certain calcium oxide / silicon

dioxide ratio, the slags self-slaking when

cooled in the air have been obtained. The

following has been obtained when floating

these slags at the pilot plant: the concentrate

containing 11-20% Сu and tails containing0.27-0.5% Сu.

This technology was recommended for

several smelters, including two foreign

ones.

Processing Nickel Matte in OFP Furnace

The studies have been conducted with

highly aggressive metallized nickel matte

containing 12–18% Ni, obtained by pit-type

reduction smelting of the oxidized nickel

ore. When processing this type of matte, thelining of the standard converter is kept max.

for 10–15 days. Naturally enough, it is

easier, more cost effectively and efficiently

to use continuous matte conversion. OFP

enables to do the process by forming ferrite

and calcic or combined slags. In such case

limestone is used as a flux, and no extra fuel

is added to the process to provide high

oxidization and temperature potentials. The

melting technology and equipment were

tested on a semi-industrial scale. As the

result of pilot smelts, the Bessemer matte

containing 68.8–75.0% Ni and 0.48–1.0%

Со and ferrite and calcic slag containing

1.4–8.4% Ni and 0.16–0,56% Со were

obtained. When smelted, nickel converts

mainly into the Bessemer matte, and cobalt

– into the slag. The depletion of the slag in

the electric furnace enables to extract even

more nickel and cobalt and obtain the

dump-grade slag (0.03% Ni; 0.02 Сo). Thistechnology is promising for nickel smelters

processing oxidized ores through

sulfidizing.

Melting and Converting when Processing

Crude Copper and Copper-Zinc in

Vanyukov’s Furnace (VF)The belit-based melting of copper

concentrates containing 15–18% Сu, 30–35% S,

25-29% Fe in a semi-industrial VF in a molten

pool with combined slags enabled to obtain a

matte containing over 70% Сu.

The researche related to developing a

technology for Ural copper-zinc concentrates

enabled to design VFs for North-Ural Copper

Melter (NRCM). The studies included the

experiments with various modes of melting

copper-zinc concentrates to a rich matte and“white matte” to form silicate slags. It was

demonstrated that in case of one-stage melting

of crude copper-zinc and production of a matte

which is similar in terms of composition to “the

white matte”, in contrast to melting crude

copper only, VF process does not require any

main flux. In such case, the zinc oxide is used

as the homogenizing agent for the slag under

high partial oxygen pressures.

The melting of combined copper-zinc

concentrates containing 8.8-15.1% Сu and 4.6-12.6% Zn enabled to obtain a matte containing

70-78% Cu and slags containing 0.7-9.93% Cu.

Zinc converts into the slag 93–94% and then

extracted by fuming.

When processing pyrite concentrates

containing 0.2-0.8% Сu, a poor matte was

obtained containing 2-10% Cu and slags

containing 0.6-0.17% Cu.

Their processing in a separate bubble unit

and dry granulation of waste slags could be one

of the optimal options for depleting the slag.

Flux-free Oxygen and Converter Technology for

Processing Crude Copper-Zink

High-temperature flux-free oxidization of an

iron-bearing matte and melt metallization

demonstrated that it is efficient for processing

crude copper-zinc.

At Gintsvetmet a 5-t converter was used to

test a copper-zinc matte containing 19.0-36.6%

Сu and 2.9-5.4% Zn and copper-zincconcentrates containing 14.0-16.1% Cu and 5.8-

9.0 Zn. The matte was fused in an ore smelting




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METALLURGY

furnace and poured into the converter

preheated to 1,150° С with natural gas and

oxygen supplied through the top tuyere. The

blowing was performed at the melt

temperature of 1,500–1,600° С by anoxygen-containing gas with concentration

75–95% O2 under pressure (6–10) –105Pa.

Zinc quickly releases immediately after

the oxygen-containing mix is blown to the

melt surface. The zinc distillation rate came

to 150–200 kg/(m2•hr) and was increasing

as the degree of flare integration into the

melt grew. To compare, zinc is distillated

during fuming at the rate of ~ 70 kg/(m2•h).

The residual content of zinc in melting

waste products came to 0.4–1.3%. Thecontent of zinc in the matte containing 57-

74% Cu came to 0.27-0.7% after blowing.

Since the amount of the dust forming

during conversion does not exceed 1–3%,

the zinc oxide content in distillation

products is 65–90%.

Flare and Bubble Melting (FBM) of

Various Types of Crude Sulfides

In this process one system combines

flux-free melting of the dried concentrate inthe vertical oxygen flare and the following

post-oxidation of the oxide and sulfide melt

in the bubbling pool installed immediately

under the flare and fluxes added to such

pool. It renders a totally different effect

which enables to intensify all the

metallurgical process stages and selectively

extract nonferrous metals, precious metals,

and sulphur into commercial products when

processing various crude materials. FBM

makes use of all the advantages of

heterogeneous-flare and bubble-emulsion

processes.

The option of distributing oxygen between

the flare and bubbling area enables to

control the process: to achieve the required

degree of desulfuration, ensure virtually

complete oxygen assimilation, distribution

thermal and gas flows in required ratios,

obtain slags with low content of magnetite

close to the equilibrium composition in thewide range of melt homogeneity subject to

high partial oxygen pressure.




Equipment Configuration and Essence of FBM Process

The figure shows the diagram of main

interactions in FBM process.

A special furnace with charged capacity of

50 t/day was used to conduct semi-industrial

tests to melt copper and copper-zinc

concentrates. The following substances were

obtained as the result of such melting:

• A matte in the flare and bubbling area

containing 77-83% Сu;

• Process gases containing, %: 16-56 SO2,

15–30 СO2, 1-6 O2;

• The slags before depletion containing,

%: 0.7-1.3 Сu, 22-26 SiO2, 10-12 CaO, 41-44

Fe, 0.35-0.9 S.

When depleting the slag in the depleting

area of the furnace with a clinker mix

obtained in the course of zinc and pyrite

concentrate production with 2:1 ratio and

bubbling the pool with an oxygen-enriched

air, slags containing 0.3–0.4% Сu and poor

matte containing 22–39% Сu are obtained.

The phased electron probe analysis of the

samples of the melt formed in the flare before

it reaches the pool and the slag from the

bubbling area before and after depletion

demonstrated that no magnetite is formed in

the flare as the content of magnetite in the

bubbling oxidizing area is 6–7%, and in the

slag after depletion – 1÷3%.

Reactions in flare

Reactions in melt

Tuyer



The test showed that the combination of

flare melting and bubbling principles in the

oxidizing area enables to:

1) Intensify “the white matte” production

(crude copper) by expanding the reaction zone

by the furnace height, distributing the suppliedoxygen, and extracting sulfur dioxide from the

gas phase;

2) Ensure uniform temperature distribution

in the reaction zone volume;

3) perform flux-free melting in the flare at

high temperatures to reduce the content of

magnetite in the slag with no risk of damaging

the furnace lining and obtaining the slag of the

required composition in the bubbling zone –

from ferriferous-silicate to ferrite-calcic – atthe melt temperatures which are standard for

bubbling processes;

4) Reduce the size of the combining zone.

Some comparative data on melting crude

copper-zinc by different methods are given

below as an example (the basic technical and

economic indicators):

Flare and Bubbling Melting:Annual production of crude copper, thous. t 93.9

Amount of zinc sublimates, thous. t 68.9Content of zinc in sublimates, % 49.5

Through extraction of copper into crude copper

(excluding burning-out), %

99.06

Through extraction of zinc into sublimates, % 90.0Content in waste slags, %

copper 0.25zinc 1.0

Extraction of sulphur into melting gases, % 70.0

Through extraction of sulphur

into metallurgical gases, %

95.2

Total volume of gases, thous. nm3/h 120.0

Content of sulphurous anhydrides in gases, % 11.8

Use of VFs in Combination with Other

Systems at Same Production VolumeVF – electric

furnace

VF – fuming

furnace

Through

extraction of

copper, %

98.8 94.0

Through

extraction of

zinc, %

73.0 85.9

The technology provides waste-free

production, high environmental performance,

fuel and energy savings, and the option of melting complex raw materials, lump reverts,

and secondary raw materials.

With this technology, Gintsvetmet and

Giprotsvetmet Institutes prepared the project

for reconstructing Almalyksky Copper

Smelter (Republic of Uzbekistan) with the

capacity of 120 thous. t of copper per year and

process regulation for creating the firstUkrainian copper smelter with the capacity of

20 thous. t of crude oil per year.

The development work of Gintsvetmet in

the field of improving autogenous smelting

described above is quite relevant today and

ready to be implemented. Gintsvetmet

Institute together with the leading design

institute Giprotsvetmet are prepared to provide

process solutions to integrate the latest

developments into the global practice of producing heavy nonferrous metals.

non ferrous melting

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