Throat Accretion Management at the Olympic Dam Flash Furnace

The Olympic Dam (OD) flash furnace (FF) smelts copper concentrates directly to a blister copper. During operation, a proportion of the smelted concentrate is entrained in the gas phase and passes through the furnace through to the waste heat boiler (WHB) forming an accretion that requires routine downtime and mechanical intervention to remove. Large throat accretions are of considerable concern due to increased risk of worker exposure to hazards and extended production downtime required to remove the accretions. Historically, the FF was taken offline every two days for approximately 90 min to allow for the safe and efficient removal of these accretion. An investigation into the thermochemical behavior of dust particles found that the size and mechanical properties of throat accretions were predominately influenced by two factors; ensuring the dust particles were fully oxidized (i.e. no metallic copper present) and dust melt liquidus above 1220°C. FactSage 8.2 was used to calculate the thermodynamic properties of the dust particles. Oxygen was injected into the settler freeboard through non-operational fuel oil burners, a minimum oxygen injection rate of 1,000 Nm³/hr of oxygen into the settler freeboard was established to ensure all dust particles were fully oxidized. And the frequency between throat cleans was established based on feed composition and operational observations during throat cleans. The improved management and forecasting of throat accretion at OD has increased the frequency between throat cleans from 2.5 to 3.3 days. Opportunities to further increase the time between throat cleans exists for specific feed compositions.