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Zincor

Located 50 km east of Johannesburg in Springs, Zincor is an electrolytic zinc refinery with the capacity to produce 110ktpa of zinc and 170ktpa of sulphuric acid. The elimination of bottlenecks and a recovery improvement project are aimed at increasing zinc production to 115ktpa by the end of 2007.

Zincor employs approximately 760 people, including contractors, and processes some 240ktpa of zinc concentrate. The zinc concentrates are supplied by Rosh Pinah (50%) and Black Mountain (30%) while 20% is imported.

Zincor is currently the only zinc refinery in South Africa. Most sales are to customers in the galvanising, zinc chemical and zinc alloy industries, clustered within a radius of 100 km of the plant. Some 25% of Zincor’s total sales are to Mittal SA and approximately 13% to Duferco Steel Processing in Saldanha Bay on the west coast of South Africa. Zincor’s pricing structures are linked to the London Metals Exchange zinc price.

The sulphuric acid produced at the plant is a superior-quality by-product and a major source of supply to the South African market.

Process

As a modern internationally competitive refinery, Zincor strives continually to achieve quality in all aspects of its operations. In so doing, Zincor maintains a sophisticated research and development programme and pursues comprehensive management of occupational health, safety and the environment. Zincor, an equal opportunity company is ISO 9001, ISO 14001 and OHSAS 18001 certified.

The production of metal at Zincor takes place in a continuous five stage process:

Roasting
Leaching
Purification
Electrowinning
Melting and casting

ROASTING

The zinc bearing raw material supplied to Zincor is in the form of a finely powdered zinc sulphide concentrate. Zinc concentrates are roasted at 950°C to convert the sulphide concentrates to zinc oxide or calcine. The sulphur dioxide gas produced during roasting is cleaned, dried and then oxidised into sulphuric trioxide. The trioxide can then be reacted with water to produce sulphuric acid, the primary by-product of zinc production.

LEACHING

Following roasting, the calcine is milled in preparation for leaching. Leaching takes place in three phases during which the calcine is dissolved in sulphuric acid to produce an impure zinc sulphate solution. During leaching, the major portion of the metallic impurities in the zinc solution is precipitated and removed by filtration. The filtered solution is then ready for further purification.

PURIFICATION

The zinc sulphate solution obtained after leaching contains impurities that are detrimental to electrolysis. During purification therefore, a series of chemical reagents is used to precipitate impurities from the solutions. Purified solutions contain approximately 140 g per litre of zinc and traces of cadmium, arsenic, cobalt and copper. Quality assurance at Zincor is such that tolerable impurity levels are measured in parts per million, necessitating exact solution chemistry and precise assaying techniques.

ELECTROWINNING

The purified zinc sulphate solution is pumped to the cell house where zinc metal is electrolytically plated onto aluminium cathodes. Banks of cells, each containing 40 cathodes are bathed in a continuous stream of the zinc electrolyte. The cathodes are removed and stripped manually of the zinc plate on a 24-hour cycle.

MELTING AND CASTING

The stripped cathode zinc is then melted in four induction furnaces at 500°C and cast into 25 kg ingots,
1 ton and 2 ton jumbos. Ingots are strapped into pallets weighing approximately one metric ton. Each pallet is weighed, batch coded and the passed into stock ready for despatch. A jumbo prealloyed furnace was commissioned in early 2005 to cater for the needs of continuous galvanising lines.

Grades

SA Code No		Zn	Pb	Cd	Fe	Sn	Cu	Al	Tl	In	TOTAL Pb,Cd, Fe, Sn, Cu, Al, Tl, In
SHG	min	99,995	–	–	–	–	–	–	–	–	–
	max	–	0,0030	0,0030	0,0020	0,0010	0,0010	0,0010	0,0010	0,0005	0,0050
Zn1	min	99,99	–	–	–	–	–	–	–	–	–
	max	–	0,0030	0,0030	0,0030	0,0010	0,0020	0,0010	0,0010	0,0005	0,0100
Zn2	min	99.95	–	–	–	–	–	–	–	–	–
	max	–	0,0080	0,0200	0,0100	0,0010	0,0020	0,0050	0,0010	0,0005	0,05
Zn4	min	98.5	0,95	–	–	–	–	–	–	–	–
	max	–	1,35	0,1500	0,04	0,02	–	0,005	–	–	1.5

Prices

Month/Year 2006	LME $ per ton	R/$ exchange rate	Rand per ton
January 2006	2,090.32	6.0859	12,721.42
February 2006	2,219.38	6.124	13,591.48
March 2006	2,416.91	6.2493	15,104.00
April 2006	3,084.78	6.0775	18,747.75
May 2006	3,565.69	6.327	22,560.12
June 2006	3,225.68	6.9828	22,524.28
July 2006	3,339.86	7.0827	23,655.23
August 2006	3,347.30	6.9382	23,224.24
September 2006	3,403.02	7.4285	25,279.33
October 2006	3,822.95	7.6435	29,220.72

Price archive

Select link to year to view prices:

2005	2003	2001	1999
2004	2002	2000	1998

Physical address	Postal address
Plover Street, Struisbult, Springs Gauteng, South Africa	PO Box 218 Springs 1560 Gauteng, South Africa

CONTACT
Bertus de Jager General Manager Tel: +27 11 812 9512 Fax: +27 12 307 3741	Owen Tennant Marketing Manager Tel: +27 11 812 9500

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