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Jul 5, 2017

Outotec Ausmelt TSL lead smelter start up

The Outotec Ausmelt TSL lead smelter at Hulunbeier, Hailar, Inner Mongolia, China, was successfully hot commissioned from October to December 2014.
Ausmelt TSL plant

The project was originally signed in 2009 and is the third TSL lead based smelter for the Yunnan Metallurgical Group  (Yunnan Chihong Zn & Ge Co.,LTD ). This third smelter is the first Outotec Ausmelt TSL that YMG has adopted and the project was signed against the background of the YMG group also signing for their second competitor-based TSL technology also located in China. The project and company formed for the Hulunbeier project, was Hulunbeier Chihong Mining Limited (HCHM) and was built with local and Chinese government incentives for industry development in the Automonous Regions and Provinces in China.

The Outotec Ausmelt TSL project in Hailar, was therefore on a greenfield site and while started in late 2009 with design and construction, the project was delayed or slowed down over many years. Finailization of licensing arrangements with local stakeholders was one reason for the delay in the overall schedule. The plant was finally cold commissioned by Outotec’s Ausmelt TSL team in March/April 2014. Operators were trained in May and five months later the Ausmelt furnace heat-up was commenced. Final license approvals were not received until around mid-October, by which time the furnace refractory had sustained a very controlled 2 week preheating.

Integrated lead plant

HCHM have constructed an integrated lead plant including a lead casting and refinery, final slag fuming, offgas cooling and cleaning, and sulfuric acid plant (SAP) operations. The lead plant incorporates a single Outotec Ausmelt TSL smelter (F1) which processes lead concentrates and lead recycles (fume, reverts) in a two stage process; smelting of lead feeds followed by the high lead slag reduction with a capacity of 60kdmt/y lead bullion. In general, a design batch cycle initially consists of approximately 5 hours of smelting (oxidizing  PbS to Pb bullion and some PbO slag). After this the process is changed to a two-stage reduction in the same furnace over a 2 hour period. In thereduction stage I, PbS and lump coal are added to reduce the PbO in slag to <20% Pb with high bullion formation followed by reduction stage II to further reduce slag to ~5% Pb using lump coal only. The bullion produced in both stages is tapped to kettles for preliminary dross removal and then cast in lead anodes for further refining. The final slag is then tapped to a small holding furnace (ESF) and later to a batch fuming furnace for final zinc recovery.

Hot commissioning

Two hot commissioning (HC) team members arrived at the site at the end of September and were joined in mid-October by a Process Control Engineer and two further supervisory Outotec HC team members. 

The hot commissioning started quickly once approvals were received with a brief slag smelting period to form a start bath of approximately 500 mm depth. During this period, HCHM added high grade sulfur concentrates to commission the sulfuric acid plant. There were some small equipment disruptions and concentrate smelting was commenced producing a high lead slag. A second cycle was commenced and the reduction stages were also implemented. A small quantity of bullion was successfully tapped from the furnace on October 25th, 2014.

Smelting rates were adjusted quickly to 25 to 30 t/h (design 18 t/h plus reverts) and the reduction stages were then optimized and settled over the following weeks. Fume recycling was commenced in smelting with the consistency improved gradually. With Outotec supervision, HCHM operators and metallurgical support team quickly learned the use of the process planning, control techniques and tools.
 
The plant was hindered by external sulfuric acid plant and downstream bullion and slag handling equipment however on the whole the majority of the furnace equipment and gas cooling/fume collection work without major impacts. Further process tuning is anticipated to be carried out in early to mid 2015 with Outotec involvement.

 Ausmelt TSL
People at Ausmelt TSL smelter (left).HCHM Lead Smelter Building (middle), Lead Bullion Tapping (right)
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