812
T. Kerry et al.
plants, there are also valuable quantities of other materials such as iron, flux, and carbon. As such, when it is possible, they are returned to the process. However, at high
levels of Zn, operational problems can occur in the integrated steelmaking process.
The most detrimental effect is the undermining of the walls of the furnaces through
Zn penetration, this can lead to localised oxidation [1]. Consequently, the amount of
Zn present in the cycle has to be limited, dusts that contain high concentration of Zn
are stored or even landfilled [2, 3].
Zn smelters face fluctuating markets for the procurement of zinc ores and can thus
face high prices. This leads to the search for secondary sources of zinc at reasonable
prices. The zinc-containing residues from steelmaking have a wide variance in zinc
concentrations with the maximum being found in EAF dust (up to 43 wt%) [3]. From
the integrated steelmaking process, however, values are much more likely to be a
maximum of a few percent with a maximum of 8–10% [4, 5]. In general, from any
of these sources, concentration of the zinc is required before it can be used within
zinc production. Furthermore, the mineralogical form of zinc is of great importance
to the zinc recovery. These dusts most commonly contain zinc in the form of ZnO or
ZnFe 2 O 4 [6–8]. Industrially, the former can be readily treated both through hydroand pyrometallurgical processes, whereas the latter is much more stable and requires
harsher, more costly treatment [9].
Commonly, thermal treatment is applied to these secondary materials with the
industry standard being a pyrometallurgical technique, the Waelz process [5]. Here,
a carbon-based reducing agent (generally in the form of coal) and temperatures of
over 1200 °C are utilised to volatilise the zinc [10], the produced vapour can then
be condensed and collected. Despite the prevalence of the Waelz kiln, there are several negatives associated with the process such as high amount of newly generated
residues and the potential loss of other valuable material [5]. Consequently, alternative approaches for managing these industrial by-products are required. One potential
approach is through recycling within the HIsarna furnace. This is an ironmaking route
composed of two units, a cyclone converter furnace (CCF) and smelting reduction
vessel (SRV). A pilot scale facility has been operating at Tata Steel Ijmuiden since
2010, in which time it has been shown that the process is highly suited to heavy
metal recovery. There is no limit on the quantity of zinc that can be input to HIsarna
and indeed the process has extremely high raw materials flexibility [11]. HIsarna is
capable of recycling ironmaking waste dusts, galvanised steels scrap, and moreover
waste materials from other industries, such as zinc production residues. With Zn
concentrations of 50% or more in the HIsarna produced dust, it can be sold directly
to Zn smelting operations [12]. Not only does this enable the reuse of a valuable
resource and therefore contribute towards a circular economy but it also contributes
to a positive environmental impact.
Investigations have been taking place into the pyrometallurgical behaviour of some
of these industrial by-products. Blast furnace (BF) dust and basic oxygen furnace
(BOF) dust along with ‘goethite’ waste from the zinc industry have all been studied.
Through an understanding of how to maximise the zinc vaporisation efficiency, the
concentration of zinc in the HIsarna off-gas system can be increased. Furthermore,
secondary material that is also rich in iron can be added to the process and from this its
T. Kerry et al.
plants, there are also valuable quantities of other materials such as iron, flux, and carbon. As such, when it is possible, they are returned to the process. However, at high
levels of Zn, operational problems can occur in the integrated steelmaking process.
The most detrimental effect is the undermining of the walls of the furnaces through
Zn penetration, this can lead to localised oxidation [1]. Consequently, the amount of
Zn present in the cycle has to be limited, dusts that contain high concentration of Zn
are stored or even landfilled [2, 3].
Zn smelters face fluctuating markets for the procurement of zinc ores and can thus
face high prices. This leads to the search for secondary sources of zinc at reasonable
prices. The zinc-containing residues from steelmaking have a wide variance in zinc
concentrations with the maximum being found in EAF dust (up to 43 wt%) [3]. From
the integrated steelmaking process, however, values are much more likely to be a
maximum of a few percent with a maximum of 8–10% [4, 5]. In general, from any
of these sources, concentration of the zinc is required before it can be used within
zinc production. Furthermore, the mineralogical form of zinc is of great importance
to the zinc recovery. These dusts most commonly contain zinc in the form of ZnO or
ZnFe 2 O 4 [6–8]. Industrially, the former can be readily treated both through hydroand pyrometallurgical processes, whereas the latter is much more stable and requires
harsher, more costly treatment [9].
Commonly, thermal treatment is applied to these secondary materials with the
industry standard being a pyrometallurgical technique, the Waelz process [5]. Here,
a carbon-based reducing agent (generally in the form of coal) and temperatures of
over 1200 °C are utilised to volatilise the zinc [10], the produced vapour can then
be condensed and collected. Despite the prevalence of the Waelz kiln, there are several negatives associated with the process such as high amount of newly generated
residues and the potential loss of other valuable material [5]. Consequently, alternative approaches for managing these industrial by-products are required. One potential
approach is through recycling within the HIsarna furnace. This is an ironmaking route
composed of two units, a cyclone converter furnace (CCF) and smelting reduction
vessel (SRV). A pilot scale facility has been operating at Tata Steel Ijmuiden since
2010, in which time it has been shown that the process is highly suited to heavy
metal recovery. There is no limit on the quantity of zinc that can be input to HIsarna
and indeed the process has extremely high raw materials flexibility [11]. HIsarna is
capable of recycling ironmaking waste dusts, galvanised steels scrap, and moreover
waste materials from other industries, such as zinc production residues. With Zn
concentrations of 50% or more in the HIsarna produced dust, it can be sold directly
to Zn smelting operations [12]. Not only does this enable the reuse of a valuable
resource and therefore contribute towards a circular economy but it also contributes
to a positive environmental impact.
Investigations have been taking place into the pyrometallurgical behaviour of some
of these industrial by-products. Blast furnace (BF) dust and basic oxygen furnace
(BOF) dust along with ‘goethite’ waste from the zinc industry have all been studied.
Through an understanding of how to maximise the zinc vaporisation efficiency, the
concentration of zinc in the HIsarna off-gas system can be increased. Furthermore,
secondary material that is also rich in iron can be added to the process and from this its