Substance description/characteristics
The substance Residues, zinc smelting is a UVCB (origin: inorganic)
Public name: Zinc ashes and drosses
| EC number: | 273-824-3 |
| EC name: | Residues, zinc smelting |
| CAS number (EC inventory): | 69029-83-0 |
| IUPAC name: | Residues, zinc melting, alloying and casting |
| Description: | Residues, zinc smelting (EC 273-824-3) are formed in manufacturing steps when zinc or zinc alloys need to be melted. Commercial grades of zinc ingots are molten at elevated temperatures at 550°C at atmospheric conditions, in a closed and ventilated furnace, alloying the melt per campaign according the specifications (quality and format) of the customer’s applications: sometimes 25 kg-ingots with 4% Al and 1% Cu for Die-casting applications, sometimes 1t -5t slabs with 0,5%Al or 0,2%Ni and minor additions of Sn and Bi for Galvanizers customers, sometimes 2t slabs with 1% Cu and minor additions of Ti for Zn-sheet applications. The by-product material “Residues, zinc smelting – EC 273-824-3”, collected once or twice per shift, contains essentially: • Zinc oxide with other metallic oxide, in variable composition coming from the not solicited, but unavoidable, oxidation of the zinc-alloy occurring at the bath surface with ambient air. • Fluxing agents ( alkali-chloride based) added on the bath surface in order to control the dross formation and some refractory traces from the furnace lining ( Ca-Mg-silicates) • Metallic zinc alloy, in variable quantities, coming from raking regularly the surface bath in order to clean it from the dross formed. This intermediate is further used in metallurgical plants for recovery of zinc and/or zinc compounds. |
| Molecular formula: | n.a. |
| Molecular weight range: | n.a. |
| Physical state: | solid at 20°C and 1013 hPa |
2. Source, process and conclusion
| Source |
Molten zinc from zinc concentrates and secondary sources |
| Process |
Commercial grades of zinc ingots are molten at elevated temperatures at 550°C at atmospheric conditions, in a closed and ventilated furnace, alloying the melt per campaign according the specifications (quality and format) of the customer’s applications. For example, 25 kg-ingots with 4% Al and 1% Cu for Die-casting applications, or 1t -5t slabs with 0,5%Al or 0,2%Ni and minor additions of Sn and Bi for Galvanizers customers, or 2t slabs with 1% Cu and minor additions of Ti for Zn-sheet applications. The by-product material “Residues, zinc smelting – EC 273-824-3”, collected once or twice per shift, contains essentially: Zinc oxide with other metallic oxide, in variable composition coming from the not solicited, but unavoidable, oxidation of the zinc-alloy occurring at the bath surface with ambient air ; Fluxing agents ( alkali-chloride based) added on the bath surface in order to control the dross formation and some refractory traces from the furnace lining ( Ca-Mg-silicates) ; Metallic zinc alloy, in variable quantities, coming from raking regularly the surface bath in order to clean it from the dross formed. |
| Conclusion |
Residues resulting from zinc smelting mainly consists of Zn and Zn compounds, further processed in metallurgical plants for recovery of zinc and/or zinc compounds. |
3. Composition of the substance
Residues, zinc smelting has 2 composition ranges, one of which has very low cadmium and nickel.
The boundary composition which represents the worse case is detailed here below.
Elemental composition - boundary:
| Core | min (% w/w) | max (% w/w) | Typical (%w/w) |
| Si | 0.28 | 0.86 | 0.62 |
| Zn | 40 | 80 | 67 |
| Al | 0 | 20 | 0.55 |
| Fe | 0 | 10 | 0.59 |
| Pb | 0 | 12 | 0.6 |
| Cd | 0 | 0.02 | 0.01 |
| Cu | 0 | 12 | 0.02 |
| Ni | 0 | 5 | 0.02 |
| Bi | 0 | 5 | 0.02 |
| Sn | 0 | 5 | 0 |
| Ti | 0 | 4 | 0.05 |
| Cl | 0 | 6.6 | 5.5 |
Mineralogical composition - boundary:
| Core | min (% w/w) | max (% w/w) | Typical (%w/w) |
| Zn | 12 | 24 | 20.1 |
| ZnO | 33.24 | 66.48 | 55.68 |
| ZnCl2 | 0 | 4.56 | 3.8 |
| ZnFe2O4 | 0 | 21.6 | 1.27 |
| PbCl2 | 0 | 16.1 | 0.81 |
| CuO | 0 | 15 | 0.03 |
| CdO | 0 | 0.02 | 0.01 |
| NiO | 0 | 6.36 | 0.03 |
| Bi2O3 | 0 | 5.57 | 0.02 |
| SnO2 | 0 | 6.38 | 0.01 |
| TiO2 | 0 | 6.67 | 0.08 |
| NaCl | 0 | 6.56 | 5.47 |
| CaSiO3 | 2.56 | 7.68 | 5.53 |
| Al2O3 | 0 | 37.8 | 1.04 |
4. Classification
| The classification is always based on the worst case. For the generic grade Residues, zinc smelting, this corresponds to: | |
|
Serious eye damage / eye irritation |
Eye damage 1 |
|
Skin sensitisation |
Skin sens.1 |
|
Carcinogenicity |
Carc. 2 |
|
Reproductive toxicity |
Repr. 1 |
|
Specific target organ toxicity - repeated (STOT-RE) |
STOT RE 1 |
|
Hazardous to the aquatic environment (acute / short-term) |
Aquatic Acute 1 |
|
Hazardous to the aquatic environment (long-term) |
Aquatic Chronic 2 |