The Ronnskar smelter even looks broad-shouldered, hunched on a low peninsula that that pokes out into the Gulf of Bothnia. It needs those shoulders to carry the expectations placed on it by
Newly spun off by parent company Trelleborg, Boliden had paid US$360 million to take over Westmin Resources in 1998; then, within three months, was hit with a disastrous tailings dam failure at its Los Frailes mine in southern Spain. Provisions for losses wiped out the company’s profits, and the market punished Boliden shares, out of a fear that the liabilities might grow larger.
Against that backdrop, in mid-1998, Boliden decided one of the best things it could do with US$245 million would be to expand the Ronnskar smelter, which had been a steady moneymaker during the company’s most difficult times.
The original Boliden deposit, about 50 km to the northwest, was discovered in the 1920s and began by shipping ores directly to smelters overseas. Boliden built its own smelter at Ronnskar in 1928 and commissioned it in 1930 to process the Boliden ores, which were being hit with heavy shipping and smelting charges. By 1950, Ronnskar counted itself among the largest copper producers in Europe, turning out 70,000 tonnes annually — about twice what Horne or Flin Flon turned out in the same period.
Ronnskar had turned in a steady US$25 million to US$30 million in earnings through the late 1990s, helping to offset significant losses in 1998. More of the same performance would be welcome.
Boliden’s reasoning was that Ronnskar enjoyed a number of advantages over its rivals in Europe: a year-round port, a large margin of revenues over costs, and an in-house source of most of its concentrate feed from the Boliden-area mines and the company’s big open pit at Aitik. Add to that a potential economy of scale in producing 71% more copper, and the company saw something it had not seen in a while — an opportunity, rather than a fire to fight.
The expansion is built around a new furnace using the
The virtue of the flash system is that the reaction, once started, generates its own heat and is essentially self-sustaining. The energy savings that result are the process’s strongest point.
Cost estimates show Ronnskar can be expected to produce copper at around US$170 per tonne, about 75% of current operating costs. The project is expected to pay for itself in six and a half years, generating an internal rate of return of 32.5%, after taxes, based on a 50% debt-to-equity ratio and a presumed cost of 5.5% for debt capital.
One furnace doth not an expansion make. The greater volume of copper coming from it compels Boliden to add capacity farther down its process stream — three new converters and a new casting plant that can produce 100 tonnes of anode in an hour, tripling the smelter’s casting capacity. Eleven more tanks were added to the Ronnskar refinery to keep up with the new production. The casting plant and the new tanks are already in operation; the first converter is scheduled to start feeding the casting buckets in June.
More copper, of course, also means more sulphur, so the smelter’s sulphuric acid plant, which captures waste sulphur dioxide, has also been enlarged. The new plant handles 280,000 cubic metres of process gas per hour.
The expanded smelter needed better shipping capacity, so the existing harbour at Skellefteahamn was dredged and the pier extended another 250 metres to allow larger bulk carriers into port. A new oxygen plant, built and operated by contractor Air Liquide, is also working.
The expansion creates some new jobs, but not many — the expansion, according to Johan Wiklund, Ronnskar’s general manager, “means bigger machines, but not more manning.” The new furnace will need 25 more staff, and the expanded tankhouse will need 15 more. Annual productivity, on the other hand, increases drastically, from 240 tonnes per employee to 360, once the expansion is complete.
Ronnskar’s new flash furnace was being bricked at the time of The Northern Miner’s visit, and will be “cold-commissioned” in June before beginning production in August.
Little other work remains on the expansion, which is meeting both its budget and its schedule; the largest job remaining is to complete the last of the new converters, which will be commissioned after the startup of the smelter.
Ronnskar’s new converters are designed to keep production moving and emissions low, with systems to feed anode scrap from casting and electrolytic tanks directly into the converter. This way, the converter need not be shut down and its sulphur dioxide emissions are lower.
Ronnskar grew up a conventional electric-furnace smelter, and is not leaving that behind despite suggestions that a full conversion to flash smelting in the expansion could have shrunk operating costs further. The chief reason for retaining the electric furnace — which dates from 1949, and was rebuilt in 1988 — is its usefulness in re-smelting copper wastes: the flash process is a marvellous energy-saver but can only be sustained by sulphide ores.
Scrap simply can’t be ignored as a material source for Ronnskar, especially when four trains a week take cathode to the Elektrokopper wirebar mill in southern Sweden and scrap can get a free ride back. Recycling is an important niche for Ronnskar, which takes about a third of the scrap on the market — its principal rival in the sector is
Ronnskar now gets about 30% of its feed in electrical and electronic scrap, and in ash and residues from metal fabricators, mainly brass mills. Even under the expansion plans, Boliden expects scrap to make up about 15% of the new feed stream.
The scrap Ronnskar receives from brass mills, along with chalcopyrite-sphalerite concentrates from the Boliden-area mines, make Ronnskar a zinc producer as well. The smelting process partitions zinc mainly into the slag, which is sent to a coal-fired fuming plant where it vapourizes and reacts with the air to form a zinc oxide clinker. The new flash furnace will also produce a zinc-bearing slag for the fuming plant.
Zinc clinker goes to the Norzink zinc plant in Odda, 75 km southeast of Bergen on the Norwegian coast. At Norzink, a joint venture of Boliden and
Even the rest of the slag has a use — it makes an acceptable fine aggregate for road construction.
Ronnskar has another electric furnace to smelt lead concentrates from Boliden’s Laisvall mine, about 250 km to the northwest. The furnace — which is used two weeks to produce crude lead, then turned over to copper recycling for two weeks — feeds a multiple-stage pot refinery and an ingot casting plant.
Anode sludges from the Ronnskar tankhouse and silver-bearing mattes from the lead refinery go to a precious metals plant that produces electrolytic silver, a palladium-platinum powder, fine gold, copper telluride, and high- and low-purity selenium.
From its earliest days, in the 1930s, the smelter had to handle concentrates with high arsenic and antimony concentrations: ores from the Boliden mine were loaded with arsenopyrite. Consequently, Ronnskar evolved as a smelter that had little trouble with “troublesome” ores, and had a head start on solving emissions problems — it was an early convert to the tall-stack principle, and, in 1953, an equally early one to capturing sulphur dioxide to make sulphuric acid.
Ronnskar’s sulphur dioxide emissions have declined steadily since the 1930s as well, from about 170,000 tonnes annually to today’s 3,000 tonnes. More strikingly, metal production has risen drastically in that time, so that sulphur dioxide emissions per tonne of metal have fallen about a thousandfold.
The good environmental performance brings a bonus: Ronnskar can handle some unusual (and potentially unpleasant) feeds without exceeding its emission limits. A case in point is its ability to recycle insulated cable and printed circuit boards, whose plastic components degrade to dioxin when smelted. Ronnskar keeps its dioxin emissions low by tight process control, which provides the high temperatures that destroy dioxin as it is being produced in the furnace. Actual emissions are down around 0.1 gram per year, a fifth of what the smelter’s regulatory approvals allow.
From the start, the expansion had to be worked around continuing production, which frequently left little room for errors in scheduling and co-ordination. Other than a short interruption in September of 1999, when the new casting wheel was installed, the smelter was able to operate on schedule even as the new facilities were being built. The existing converter house remained in operation while the new one was built around (and above) it — then, when the new building was complete, the old one was demolished inside it, while production continued.
The whole expansion has relied on proven technologies, particularly the Outokumpu flash process, and that has allowed the new components to be brought on-stream as they have been built. The expansion had another advantage: it provided an opportunity to build a uniform control system through the whole plant, which will be operated from a control-room between the two furnaces.
Moreover, the biggest job in bringing Ronnskar’s annual copper production above 300,000 tonnes would be to build a new tankhouse and expand the sulphuric acid plant; most of the other components are in place.
Once the new Ronnskar process stream is running, it will have no shortage of feed. Aitik, Garpenberg and the mines of the Boliden area will continue to ship concentrate, and recyclers will continue to ship scrap, but Boliden has also concluded long-term contracts for concentrate with four copper mines — in Chile and elsewhere on the Pacific Rim — and with concentrate brokers. External concentrates, which now make up about a quarter of Ronnskar’s copper feed, will dominate, making up 55-60% of the feedstock once the expanded smelter is in full production.
Could you please send me the e-mail address of Ronnskar right contact person
responsible for Metallurgical Sulphuric Acid plant