Delivery Concentrates are delivered to us Concentrate is generally made up of

Ores are concentrations of minerals in rock that have an economic value. Ore is crushed and treated to upgrade the mineral. The concentrate is then sent to a smelter for processing.

Around 500,000 Tonnes of concentrate are delivered to our wharf every year and are currently supplied from mines in Rosebery on the west coast of Tasmania and the Century Mine in Northern Queensland, as well as minor amounts from other sources.

Oxides from recycled metal materials that have a high zinc content (for example the dust that is generated from the production of steel) are added back into the process. Our goal is to continually increase recycled materials in our feedstock, which will in turn ensure sustainable production.

Concentrates are delivered by ship and unloaded into covered stockpiles, the concentrate is transported 800m to the roaster by a series of conveyor belts.

Onto Roasting
Roasting Roasting

Conveyor belts feed the concentrate into one of the two roasting furnaces.

Concentrates are roasted at 930°C to 960°C in a fluid bed roaster* and turns into a material that will dissolve (calcine).

The steam produced from the roasting furnace is captured and used to heat the acid in leaching.

Calcine travels by conveyor belt to leaching.

*A fluid bed roaster is like a giant wood heater that the concentrate burns inside of, causing a chemical reaction and creating calcine.

Onto Leaching
Leaching Leaching

Leaching dissolves the zinc out of the concentrate and removes some impurities such as iron, leaving a zinc rich impure solution.

Onto Purification
Purification Purification Purification

The impure solution from leaching then goes through the purification process. By adding pure zinc dust (that comes from casting) to the impure solution, the remaining impurities are removed as a solid caused by the zinc dissolving.

Onto Electrolysis
Electrolysis Electrolysis

The zinc contained in the pure solution is deposited onto the aluminium cathodes by passing electric current through both the cathodes and lead anodes. This process is called electrowining. The cathodes are removed from the cells and the zinc sheets are stripped from the cathodes and sent to casting.

283, 000 Tonnes of cathode zinc was produced in the cell house in 2011.

The Hobart smelter is one of the world's most efficient zinc producers despite technology at the site, particularly the Cell House, changing very little since it was built in 1921.

Through creativity and innovation, constant efficiency improvements have seen the amount of cathode zinc that can be produced double since 1969.

Onto Casting
Casting Casting

Cathode zinc from electrolysis is melted at 550°C in induction furnaces. The molten zinc is cast into different shapes such as 10Kg or 25Kg ingots or 1 Tonne jumbo blocks.

Most of Nyrstar Hobart's finished product is exported to Asia.

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