BIG RIVER ZINC (BRZ), ILLINOIS, USA

Big River Zinc (BRZ) is an electrolytic zinc refinery located 3 km south east of St Louis. BRZ was built in 1929 to service the production of concentrate from what was then one of the most prolific zinc mining areas in the USA.  The plant has been modified and expanded many times so that it had become the second largest zinc smelter in the USA (100,000 tonnes per annum). 

 

View from the South-East towards the Mississippi and Saint Louis

 

Korea Zinc purchased the plant in 1997 for US$50 million, and over the course of the next few years undertook a major US$80 million automation and refurbishment exercise that led to a 25% reduction of the workforce. As a result of the very low zinc prices experienced at the turn of the century, in 2005 the last of the local zinc mines closed. BRZ had to find new sources of concentrate at a time when spot prices were very unattractive, as a consequence the plant could not be worked profitably and operations were suspended. 

 

In May 2006, ZincOx purchased BRZ for US$14 million, with the intention of using it to recover metal as part of the company’s recycling strategy. Since the purchase, BRZ has been on care and maintenance.

 

Initially ZincOx planned to treat the EAFD by redeveloping BRZ through the construction of a new leach and purification plant using solvent extraction. ZincOx’s management team were confident of this technology due to their experience at Skorpion Project, in Namibia where Tecnicas Reunidas SA were critically involved in the success of the project. Tecnicas Reunidas is a world leader in zinc solvent extraction technologies and provided and licensed the zinc solvent extraction process now in full-scale operation at Skorpion. At the current time, ZincOx does not intend to use the solvent extraction process for its project in Big River. This is because halides can be removed by washing and the more complex and expensive solvent extraction route can be avoided (see Recycling section).

 

Ultimately the plant will be refurbished to produce metal from the ORP concentrate.   Initially, however, capital costs can be reduced by simply using the site to wash the halide bearing concentrates produced by the recycling business.  

 

The disposal of effluent containing chlorides and fluorides was fully permitted at BRZ and washing activities of this nature have been undertaken for several years. The discharge of water containing these elements is not generally possible in the USA, so that the ability to carry out such practice is a major advantage of the BRZ site.

 

The washing of the concentrate from ORP uses conventional equipment and is carried out at high pH to prevent zinc dissolution. Waste water will be purified before being discharged. The washed concentrate will be dried before being shipped to third party smelters. In the meantime the washing of a small quantity of oxide concentrate for third parties has recently recommenced using the existing washing facility.

 

The purity of the washed concentrate is such that it could be fed directly into the leach circuit without prior roasting and using conventional purification. A study to evaluate the potential to restart the electro-refinery based on this concentrate and conventional sulphide concentrate is underway.