| Processing Plant Emissions | WNP Processing Plant Air Discharge Assessment | 4397169-66885702-113 | 16/06/2022 | 7 Sensitivity: General Table 2-6. Summary of estimated maximum annual mercury emission rates (kg/year) for an ore processing rate of 2.25 MTPA Source Mercury emission rate - no emission controls) (kg/year) Mercury emission rate – with retort oven (kg/year) Electrowinning 5.38 5.38 Oven 99.04 1.29* Furnace 161.07 2.60** Carbon Regen 122.12 122.12 Total 387.61 131.39 *(99.04kg/hr+161.07kg/yr) x 99% x 0.5%, **(99.04kg/hr+161.07kg/yr) x 1% 2.4 Emission of Other Metals Metal emission rates during smelting operations were measured at the plant during the February 2021 emission testing programme9. Table 2-7 summarises the reported emission rates and concentrations of the metals in the discharged exhaust gases. Table 2-7. Selected metal emission rates (g/h) and stack discharge concentrations (µg/m3) discharged from the Electrowinning Stack and Gold Room Furnace Stack - 2021 emission test programme results Metal Electrowinning Stack Oven/Furnace Stack Discharge concentration (µg/Nm3) Discharge rate (g/h) Discharge concentration (µg/Nm3) Discharge rate (g/h) Arsenic 0.33 0.0009 0.16 0.002 Cadmium BDL* (<0.002) BDL* (<.00005) 7.84 0.0979 Chromium 0.75 0.0019 0.61 0.0078 Copper 6.18 0.016 4.97 0.063 Manganese 1.37 0.0036 0.37 0.0046 Nickle 4.91 0.013 0.06 0.0008 Lead 0.97 0.0025 9.88 0.124 Selenium 0.36 0.0009 39.19 0.494 *BDL = below detection limit Emission testing of the metals discharged from the oven/furnace stack also occurred in 2009. The results of testing are reported in the 2012 air quality assessment10. A comparison of the hourly emission rate from the 2009 and 2021 testing programme are shown in Table 2-8. The results show that 2009 metal emission rates were generally lower or comparable to the 2021 emission rates. The exception is nickel, with the 2009 emission rate approximately 66 times higher than 2021 emission rate. 9 WaterCare Laboratory Services. Oceania Gold Waihi: Selected Metals – Electrowinning and Gold room Furnace Stacks, February 2021. 10 Newmont Waihi Gold: Air Quality Implications of Underground Mining in the Golden Link Project Area. Report prepared by K Rolfe, March 2012.
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