RETOOLING MOTHER INCO; INCO employs far fewer Sudburians than a

Inco is taking an innovative approach to contracting work on a $500-million mill rationalization and flash smelting construction project approved by the company in 1988. By putting small contracts out for tender, the company is saving a bundle and putting smiles on the faces of a lot of Sudburians to boot.

“We are structuring the contracts into packages in such a way that small local contractors can handle them,” Inco’s project manager Peter Garritsen told us on a recent site visit. “We could group more work together, but that would likely exclude local contractors from the bidding process. This way, local companies have a chance to bid even though they are generally smaller than construction companies from southern Ontario.”

As it has turned out, most of the 10 contractors chosen so far (which hold 17 contracts) are Sudbury-based, much to the delight of local companies and city council. More contracts, worth several millions of dollars each, will be let over the next four years as the company races toward the 1994 deadline (imposed by the Ontario government) for reducing sulphur dioxide gas emissions by about two-thirds.

We got a sense of the hustle and bustle surrounding the project when we visited the smelter project in Copper Cliff. The first of two new flash furnaces will begin smelting nickel concentrates from the Clarabelle mill in 1991 (and bulk copper/nickel concentrates in 1993). Engineer Victor Englesakis, Inco’s superintendent of project services, said engineering work on the mill program is 90% complete compared with about 30% as regards the smelter. Fluor – Daniel – Wright has engineering procurement and con struction management responsibility for the milling program at a cost of $69 million. Davy Canada is the overall project manager responsible for the smelter program, including procurement and the bulk of the engineering work. Hatch Associates is responsible for furnace design and the copper smelting revisions, including a new flash smelting vessel. Canadian Liquid Air and Fenco Engineers were awarded turn-key contracts for the oxygen and acid plants respectively. The combined projects employ nearly 400 people from outside engineering consultant firms. Actual construction work employs about 220 people at the smelter and about 100 at the mill, Englesakis said.

A huge construction crane had been erected and the smelter’s first flash furnace foundation was being poured during our visit. Most of the foundation work had been completed for the acid plant. Construction of the oxygen plant will start this spring, Englesrakis told The Northern Miner Magazine.

“It has been an extremely hectic pace,” Garritsen said. “We’re driven by a government mandate and the schedule is very tight. But so far, financially and in terms of the schedule, we’re on track.”

Flash smelting is not a new technology; the first such smelter was installed 40 years ago. There are two competing designs — one by Outokompu and one by Inco. In North America, Inco has two flash smelting furnaces operating in the U.S. and one in Canada whereas Outokumpu has one furnace operating at Magma Copper’s San Manuel smelter near Tucson, Ariz. As must be expected, problems arise with technological conversions. The 2,700-tonne-per-day flash furnace at Magma Copper’s smelter, for example, was dogged with design and operating problems for a whole year, according to Magma.

Flash smelting technology is considered desirable by companies because of its energy efficiency and its ability to efficiently capture sulphur dioxide gasses. Dried concentrate, along with commercial oxygen, is injected into the furnace through a flash gun. The concentrate ignites (or oxidizes) in an exothermic reaction, smelting the concentrate almost instantaneously.

Inco’s existing flash smelting furnace has operated in the company’s copper smelter for more than 20 years. That unit ran a full-scale operating test on bulk (nickel/copper) concentrates from the mill, Garritsen said. Metallurgical results were satisfactory and Inco has decided to go ahead with a plant to convert from 24 Herreshoff roasters and two reverberatory furnaces to two new flash furnaces. Although some flash smelting installations have experienced start-up problems, Inco has confidence in the technology, largely because of the proven record of the company’s copper flash smelting process.

The first step is to demolish one standby reverberatory furnace to make room for the first flash furnace. Construction has been scheduled to avoid interrupting nickel production. To construct the second flash furnace, an operating reverberatory furnace will be demolished after the first flash furnace is operating. The first new flash furnace will treat nickel concentrates, then, when the rationalization program nears completion, will begin treating bulk copper/nickel concentrates. Construction has been scheduled in such a way as to allow the company to convert from one technology to the other without affecting production.

To supply the oxygen required for two flash furnaces (each of which is rated at 2,300 tonnes of concentrate per day), a 550-tonne-per-day oxygen plant is being constructed. Inco’s existing oxygen plants currently produce about 1,300 tonnes per day. To handle the off gases from the furnaces, which will contain about 70% sulphur dioxide, a large acid plant designed to handle 2,900 tonnes per day is being built. Huge acid storage tanks are also being erected. These two plants should be operating when the first furnace is commissioned in 1991.

Once completed in 1993, the new smelting process will result in a 20% increase in productivity to about 3,000 lb. of copper and nickel per manshift. The company also estimates energy consumption will be cut in half to 4,500 British Termal Units per lb. of copper and nickel produced.

Clarabelle Mega-Mill

Inco now operates three mills in the Sudbury Basin — the Frood Stobie, the Clarabelle and the Copper Cliff. When expansion of Clarabelle is complete, all of Inco’s Ontario division ore will be treated at that facility. The 16,000-tonne-per-day Frood/Stobie mill will then be mothballed.

Ed Cade, manager of field construction for Fluor Daniel Wright said the Clarabelle mill expansion is about half finished. Bechtel Canada built the Clarabelle mill in 1971, with a rated capacity of 32,000 tonnes per day. Currently, the mill processes about 22,000 tonnes per day. When expansion is completed in 1992, capacity will be 36,000 tonnes per day. “The project has been pretty tight,” Cade said. “We’ve been pushing the engineering side pretty hard. It’s been good for us.”

George Caughell, Inco’s milling rationalization superintendent and Eugene Kautz, electrical instrumentation superintendent for Fluor- Daniel-Wright, showed us around the mill. The highlight is a 9.8-metre-diameter semi-autogenous grinding (sag) mill manufactured by Boliden Allis. “We have had to switch some of the machining (of mill components) to the U.S. from Europe because of delays in Europe,” Caughell explained. “But other than that, we expect all the components to arrive on schedule, ready for assembly sometime this summer.”

The mill building has been extended to accommodate the big new grinding mill and foundation work inside that extension was under way at the time of our visit. Contractors blasted away about a metre of oxidized caprock for a solid surface from which to work. Trow Engineering is the geotechnical consultant on the foundation work. A hole has been left in the end wall of the building for mill component access. The brick wall between the new extension and the existing mill building was to be demolished within three weeks of our visit. An existing 41-tonne overhead crane from the Clarabelle mill will travel to the mill extension for the sag mill assembly work. A 14-tonne Demag overhead crane has been installed in the mill aisle for routine grinding area maintenance work. Canadian General Electric is manufacturing the twin-drive 4,100-kw motors for the sag mill. Cyclones will be manufactured by Technequip of Weston, Ont.

An 11,000-tonne-capacity concrete coarse ore bin is also well advanced. Ore is either trucked to the mill or brought in by rail car and dumped in a tipple building, two cars at a time, through a grizzly with openings 25 cm across. The ore falls into a 27,000-tonne coarse ore bin. Six apron feeders reclaim the ore from the bin and discharge it on to two parallel 1.1-metre-wide conveyor belts. These belts deliver the ore 580 metres up an incline to a 2,700-tonne crusher feed bin. In the crusher building, ore is fed on to six crusher lines. Each line consists of double-deck screens, a standard 2.1-metre cone crusher and a 2.1-metre shorthead cone crusher, each driven by a 225-kw motor. Fine ore is then conveyed to a 9,000-tonne storage bin in the mill building. Crushed ore is ground to 15% minus 65 mesh in four rod mills and six ball mills, all 4.1 metres in diameter and 5.5 metres long and driven by 1,490-kwmotors. All mills discharge into a common head tank.

When the project is completed, only two rod mills and three ball mills will remain in the conventional primary ore grinding circuit. Two rod mills will be converted to ball mills to service the final grinding of sag mill discharge along with one existing ball mill. Two other ball mills will be used for pyrrhotite reginding. The sag mill will handle about 60% of the ore, with the other 40% being handled by the remaining sections of the existing crushing and grinding circuit.

Major changes are also under way in the flotation area of the Clarabelle mill. First of all, Inco has decided to increase flotation capacity but will actually free up floor space now devoted to flotation equipment. This will be accomplished by removing 12 banks of twenty-two 2.8-cubic-metre flotation cells and replacing them with five banks of eight 38-cubic-metre flotation cells, manufactured by Dorr Oliver Canada. A test line of eight Outokumpu flotation cells (not flotation columns) has been operating since 1987 with good results. To accomodate the new cells, reinforced concrete columns had to be installed to support the additional weight.

A bulk copper/nickel concentrate is produced using sodium amyl xanthate and Dowfroth SA1263 frother (the company does not divulge reagent consumption rates).

Since the Copper Cliff mill, about 1.6 km away, will no longer be required to produce separate nickel and copper concentrates, the pyrrhotite rejection circuits in that mill will be relocated to Clarabelle. Floor space freed up by going to the larger flotation cells will facilitate the move. This circuit includes existing 2.8-cu-metre flotation cells and revised, wet, high-intensity, magnetic separators.

Two new Eimco thickeners, 25 metres in diameter, are being constructed outdoors as part of the pyrrhotite rejection circuits. The lower portion of units will be insulated, but the upper portion will be allowed to freeze over during the winter months. Finally, two existing ball mills will be used for regrinding pyrrhotite. These mills will operate in closed circuit with appropriate cyclone classifiers.

Although the Copper Cliff metallurgical circuits will become redundant in 1993, the mill will continue to operate as a dewatering facility. The final concentrate will be filtered and the filter cake will be conveyed to the smelter where it will be dried in new, gas-fired, fluid bed driers, manufactured by Dorr-Oliver.

Computer Controls

A computer control system, manufactured by Foxboro Canada, is being installed in the Clarabelle mill. Programmable “logic controllers” from Canadian General Electric have been chosen for mill-wide use. These units will communicate via a “data highway” to a master control computer, a DEC PDP 11/84, in the control room overlooking the mill floor. The system provides a graphic depiction of the entire mill circuit in full color and allows the operator to zoom in for more detailed information on a particular piece of equipment by touching the graphic representation of that piece of equipment on the computer screen. The entire electronic monitoring and control system is protected from electrostatic spikes in the power supply, known as transients, by an uniterruptable power supply unit manufactured by Exide Electronics. It is installed at the power inlet box.