Process

Lead sulphide concentrates are sintered at high temperature into a lump form or sinter. Sulphur is oxidised to sulphur dioxide in a gas stream that is cleaned and processed to make sulphuric acid.

The sinter and coke are charged to a lead blast furnace that produces a crude lead bullion and slag and the bullion is then refined to remove impurities including copper, arsenic, antimony, bismuth, silver and gold.

Metallic copper is then produced through leaching, solvent extraction and electrowinning. Silver and gold are produced as refined and semi-refined products, respectively.

The blast furnace slag is fumed to recover zinc and lead as impure oxides. These oxides are then processed by leaching, solution purification and electrowinning to make market zinc metal, in a similar manner to the RLE process.

Operations

Although historically the majority of concentrates were sourced from the Broken Hill and Endeavour mines, the reduced availability of Broken Hill concentrates in recent years has led to an increase in supply from other sources, most notably Cannington, Rosebery and Century.

Currently, Port Pirie processes all of Rosebery's lead concentrates and a significant proportion of Century's lead concentrates.

In addition to processing lead concentrates, Port Pirie also processes around 110,000 tonnes of by-product residues which it sources from Hobart and from its own historic stockpiles.

The residues provide Port Pirie with an almost costless source of feedstock which contains over 17% zinc.

Currently, Port Pirie's capacity limits the quantity of residues it can treat and the excess received from Hobart is stockpiled on site. Plans to increase Hobart's proportion of Century concentrate are key to ensuring Port Pirie is able both to treat Hobart's residues and meet the EPA's target to eliminate all on site residue stockpiles by 2020.

Production

Following an improvement program that targeted plant availability and operating efficiency, Port Pirie's lead production capacity was approximately 270,000 tonnes peryear. The closure of the Cockle Creek smelter in 2003, however, removed Cockle Creek bullion as a feedstock, effectively limiting the plant capacity to 245,000 tonnes. Zinifex is currently evaluating a number of options to increase the blast furnace capacity.

The current zinc production facilities have a capacity of 43,000 tonnes per year of SHG and zinc alloys, which is fully utilised. Port Pirie produces approximately 95,000 tonnes per year of sulphuric acid, which is sold to a global acid marketing company under a long-term contract.
Environmental Management

Port Pirie works closely with and supports the local Environmental Health Centre to minimise potential health impacts of metals in the community. Community lead in blood levels in children are now at less than half the level that they were in the mid 1980's. Our aim is to progressively reduce lead in blood levels such that ultimately all children meet the national goal of 10 micrograms per decilitre.