| Dispersion Modelling Methodology | WNP Processing Plant Air Discharge Assessment | 4397169-66885702-113 | 16/06/2022 | 15 Sensitivity: General Trace amounts of metals are also expected to be emitted from the carbon regeneration stack. However, since no emission testing of the carbon regeneration stack has been undertaken these discharges have not been included in the dispersion model. Table 5-3. Modelled non-mercury metal annual average emission rate (g/s) Contaminant Electrowinning Stack (g/s) Oven/Furnace Stack (g/s) Arsenic 0.00000025 0.000000056 Cadmium 0.00000014 0.000027 Chromium (VI) 0.00000053 0.00000022 Manganese 0.0000010 0.0000013 Nickle 0.0000036 0.00000022 Lead 0.00000069 0.000034 Selenium 0.00000025 0.00014 5.6 Modelled Emission Sources A summary of the modelled discharge parameters for the modelled emission sources is show in Table 5-4. The modelled emission parameters for the electrowinning stack and the combined oven/furnace stack are derived from the results of emission testing conducted by Watercare Laboratory Services in February 202120. The stack heights have been derived from the site plan provided by OGNZL. The air discharge rate from the carbon regeneration vent has been estimated by OGNZL to be approximately 2,000 m3/hr. The discharge temperature and the height of the discharge vent have also been estimated from information provided by OGNZL. The sensitivity of model prediction to these assumptions is provided in Appendix D. A rain-cap is located on top of the oven/furnace stack and carbon regeneration stack discharges horizontally from the side of the building. Both sources have been simulated in CALPUFF assuming the discharges have no vertical momentum. The buoyancy of the emission plumes determines plume rise. Table 5-4. Summary of modelled emission parameters Source Stack height (m) Stack Diameter (m) Discharge velocity (m/s) Discharge temperature (°C) Electrowinning 8 0.2 26.7 31.6 Oven / Furnace 8.5 0.756 9.2 34.5 Carbon Regeneration 12.5 0.15 30.4 60 5.7 Meteorological Input File Accurate atmospheric pollutant dispersion modelling requires good meteorological information that is representative of dispersion conditions near the emission sources, which is then processed into a format that 20 Oceana Gold Waihi – Selected Metal – Electrowinning and Goldroom Furnace Stacks. Report prepared for OGNZL by Watercare Laboratory Services, February 2021
RkJQdWJsaXNoZXIy MjE2NDg3