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Zinc and lead oxide and sulphides

Just like stainless steel plants generate dusts and fumes by virtue of their electric-arc furnaces, so steel plants and scrap metal recycling operations generate similar dusts and fumes but, although devoid of nickel and chromium, these are usually rich in zinc and, to a lesser extent, lead.

Since these dusts pose a major environmental hazard, there is obviously much pressure to find a reliable and cost effective process that would alleviate the problem. In this regard, AMRT applied its technology to such a dust on behalf of a scrap metal recycling plant based in Israel. Several tons of this dust/fume mixture were processed through AMRT’s 0.5 MVA melt reduction test furnace which produced the following results.

 

AMRT melt reduction furnace technology as applied to a dust/fume mixture ex a metal recycling furnace located in Israel

 

Furnace input

Furnace products

 

Furnace dust
(%)

Metal
(%)

Slag
(%)

Gas
(% by volume)

Fe

29

88.5

0.39

 

Zn

26.6

0.28

0.31

6.8

Pb

2.1

4.09

0.07

0.1

Ni

0.01

0.03

0.00

 

Mn

2.3

1.8

6.00

 

SiO2

3.9

 

36.82

 

CaO

6.3

 

20.38

 

MgO

3.2

 

10.75

 

Al2O3

1.0

 

6.06

 

Cr2O3

0.3

 

1.07

 

Na2O

0.01

 

0.08

 

S

0.54

1.43

0.2

 

C

0.1

3.08

 

 

Cl

0.2

 

0.67

 

CO2

 

 

 

21.0

H2O

1

 

 

0.9

Of note was the generation of an inert environmentally-acceptable slag, a metal product, which itself is chemically inert, and where the bulk of the zinc was eventually collected, in the form of zinc oxide, in an adjoining bag house by virtue of it having been evaporated in the melt reduction furnace. The chemical reactions taking place in the reaction zone were then:

ZnO + C = Zn + CO

PbO + C = Pb + CO

Fe2O3 + 3C = 2Fe + 3CO

which drew 1500 kWh per metric ton of dust in electrical energy. Whereupon on contact with the surrounding air, the oxidation of the volatilized zinc to zinc oxide fume was effected; i.e. by the reaction:

Zn + ½O2 = ZnO

The zinc oxide product that was subsequently extracted from the bag house was of a grade (79% ZnO) that was sufficient for it to be of commercial value.

Examples of materials that have been produced by or processed in AMRT’s melt reduction furnaces are:

Copper

Cobalt

Nickel

Tin

Zinc and lead oxide and sulphides

Ferrochromium

Ferromanganese

Ferrotitanium

Precious metal-bearing wastes

Ancillary processes and procedures associated with AMRT’s furnace operations

 
 
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