Choice of emission factors

TIER 1 METHOD

The emission factor for the pyrometallurgaical process (Imperial Smelting Furnace) is an aggregate, weighted emission factor encompassing both primary and secondary zinc production in Europe (Sjardin, 2003), No data was available to determine an emission factor for the electro-thermic process. An emission factor based on the amount of coke consumed per tonne of EAF dust consumed in a Waelz Kiln furnace was developed based on the materials balance provided by Viklund-White (2000), wherein Viklund-White finds that 400 kg of coke are consumed for every metric tonne of EAF dust consumed.

Table 4.24

Tier 1 CO2 emission factors for zinc production

Process

Emission Factor

(tonne of CO2/ tonne zinc)

3.66

Derived from Viklund-White C. (2000) The Use of LCA for the Environmental Evaluation of the Recycling of Galvanized Steel. ISIJ International. Volume 40 No. 3: 292-299.

Pyrometeallurgical (Imperial Smelting Furnace) (tonne of CO2/ tonne zinc)

0.43

Sjardin 2003. CO2 Emission Factors for Non-Energy Use in the Non-Ferrous Metal, Ferroalloys and Inorganics Industry. Copernicus Institute, Utrecht, The Netherlands. June 2003.

Electro-thermic

Unknown

(tonne of CO2/ tonne zinc)

1.72

default factor is based on weighting of known emission factors (60% Imperial Smelting, 40% Waelz Kiln)

TIER 2 METHOD

The Tier 2 method requires the calculation of a country specific emission factor based on the total amount of reducing agents and other carbon containing process materials used for zinc production in the country. These country specific emission factors should be based on aggregated plant statistics on the use of reducing agents, furnace types and other process materials of interest. An emission factor was developed based on the amount of metallurgical coke consumed per tonne of EAF dust consumed: 0.4 tonnes coke/ tonne EAF dust consumed (Viklund-White, 2000). If activity data are available, an emission factor of 1.23 tonnes of EAF dust per tonne of zinc could be used to calculate emissions. When producing zinc from EAF dust in a Waelz Kiln furnace, the complexities of the process suggest that emission factors are more accurate if they are based on the amount of EAF dust consumed rather than the total zinc produced . This is because the amount of reduction materials (metallurgical coke) consumed is directly dependent upon the amount, and zinc content, of the EAF dust consumed. Weighing equipment is used in the Waelz Kiln process to control the amount of metallurgical coke entered into the kiln (Sjardin 2003; European IPPC Bureau 2001).

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