Annex 23 Complementary information to source category 2h Brass and Bronze Production

Overview of recent revisions

All PCDD/PCDF emission factors are confirmed for this source category. A new HCB emission factor is proposed with a medium level of confidence:

Table III.23.1 PCB emission factors for source category 2h Brass and Bronze Production

2h Brass and Bronze Production Emission Factors (µg TEQ/t brass/bronze)
Classification Air Water Land Product Residue
1 Thermal de-oiling of turnings, afterburner, wet scrubber 9,400        
2 Simple melting furnaces          
3 Mixed scrap, induction furnaces, fabric filters 9,400        
4 Sophisticated equipment, e.g. induction ovens with APCS          

Derivation of emission factors

Release to Air

Measured PCDD/PCDF data from brass production are available from the Thailand sampling program (UNEP 2001, Fiedler et al. 2002). The plant consisted of a small, batch-type smelter for primary and secondary brass production. The brass from the smelter was cast manually into bars, which were then rolled into coils for different products. The furnace was heated with about 30 L/h low sulfur, heavy fuel oil. The furnace was operated on a 250 kg/batch discontinuous mode during one day shift. The flue gases from the furnace and several surrounding areas pass a wet scrubber and are then discharged through the roof via a steel stack. Emissions to air may arise from smelting processes and melting of mixed scrap. The stack concentrations from the secondary brass smelter in Thailand ranged between 0.13 and 0.21 ng I-TEQ/Nm³ with an average of 0.15 ng I-TEQ/Nm³ at the actual operating O2 concentration of 19%. This concentration corresponds to an emission factor of 11 μg I-TEQ/t of brass (11 μg WHO-TEQ/t). Hence, an emission factor of 10 µg TEQ/t is assigned to class 2.

Emission factors developed for classes 1 and 3 in the 2005 version of the Toolkit have been confirmed by a Japanese study which derived an emission factor of 1.7 µg TEQ/t from 16 measurements (Iwata et al. 2008). In addition, the emission factor developed for class 4 in the 2005 version of the Toolkit has been confirmed by data from New Zealand. Measurements carried out on an induction furnace equipped with a bag filter showed concentrations ranging from 0.0053 to 0.017 ng TEQ/Nm³, corresponding to an emission factor range of 0.03 to 0.14 µg TEQ/t (Merz 2004).

As far as HCB is concerned, the Japanese study provides an emission factor value of 9,400 µg/t, based on the same 16 measurements. This value is proposed as a Toolkit emission factor for classes 1 and 3.

Release to Water

A release may occur if effluents are discharged. The source of any effluent from the process should be noted.

Release to Land

No release to land is expected.

Release in Products

Levels of PCDD/PCDF in refined brass are not relevant.

Release in Residues

Residues from gas cleaning as well as in sludge from wet scrubbers, if present, are expected to contain PCDD/PCDF. The PCDD/PCDF concentrations in the sludge samples taken from the clarifier of the water treatment system of the wet scrubbers were rather high with 8,683 and 8,567 ng I-TEQ/kg d.m., respectively. In most countries, residues from such processes or with such concentrations would be classified as hazardous waste. The amount of sludge generated was low but could not be quantified. As expected, the slag sample from the furnace exhibited a low concentration of 13.6 ng I-TEQ/kg (UNEP 2001, Fiedler et al. 2002). There is still insufficient information to provide emission factors for solid residues.