IOC’s quest for quality; With the outlook for iron ore more

Gold is for the mistress,

Silver for the maid,

Copper for the craftsman, cunning in his trade.

“Good,” cried the Baron

sitting in his hall,

“But Iron, COLD IRON, is master of them all.”

— Rudyard Kipling

The Iron Ore Co. of Canada (IOC) is on a spending binge. Its market has been under siege from international competition, mainly from Brazil, since the early 1980s. That competition has encouraged our largest iron ore miner to invest heavily in technology to lower costs and raise the quality of its products. Now, in one of its biggest spending sprees, the U.S.-controlled company (34.52% Bethlehem Steel, 28.14% M.A. Hanna, 19.96% National Steel, 11% Labrador Mining & Exploration and 6.38% Dofasco Inc.) is pouring tens of millions of dollars into new pit and milling equipment — and even diamond drilling — to define new open pit reserves. How much the company spends over the short term will depend on the direction of steel markets in the next two years.

Some say spending is long overdue. Built with early 1960s technology, IOC’s Carol Lake operation, near Labrador City, Nfld., is straining to produce 10.5 million tonnes of iron ore pellets and five million tonnes of concentrates (for sinter sales) per year with a reduced workforce of 1,900. In order to produce profitably at that level, the company has to increase the availability of its mining equipment and create the operating flexibility in its two processing plants to prevent costly shutdowns due to unscheduled maintenance. But technology is only part of the solution.

Tapping into the ingenuity of its workforce is another important way the company is working to meet its production target. Maintenance workers in the pit are being asked to take more responsibility and concentrator operators are involved in an internationally renowned Safety Training Observation Program (STOP), developed by chemical giant Du Pont.

IOC’s new capital spending isn’t an isolated occurrence. Two other Labrador Trough producers are investing heavily in equipment and employee participation programs. Those companies, Quebec Cartier Mining and Wabush Mines, are two of only three other iron ore producers in Canada; Stelco in Wawa, Ont., is the third.

How did IOC survive the 1980s? What do its employees have to do to keep alive their mine and their two communities (Wabush and Labrador City) when iron ore is fetching only US$31 per tonne.

“We can’t revert to the complacency of the 1970s,” director of public and government relations Brian Duplessis told The Northern Miner Magazine on a 2-day visit. “Quality is going to be the key to our success in the 1990s.”

Mine-Planning and Grade Control

In the pits, where 37 million tonnes of ore and four million cubic metres of waste rock are moved each year, quality means ore-blending. And ore-blending is going to be a big factor in the years ahead, said mine manager Stephen Bond. A recently installed, computerized, mine-planning system has already served to increase blending efficiency. Senior Mining Engineer David Mitchell has been working the system for about a year. “We looked at everything that was available on the market, but the q-pit system (developed at Queen’s University) was most suitable for our orebody,” Mitchell explained, as he snuggled up to the keyboard of a workstation to demonstrate. “Many of the other so-called mine-planning systems are actually mine exploration systems. We wanted something that could mimic the day-to-day activities of a mine-planner and this system does just that.”

Mitchell can do a complete mine plan for one year in moderate detail in about half a day. This compares favorably with the two to three days required to do the same work on paper. Mitchell also does 3-month, 3-year, 10-year and 15-year plans on the system. (Quebec Cartier also uses Q-PIT)

The engineering department has also begun to use an ICEM computer- aided-design system using Control Data software for electrical and mechanical engineering work.

Ioc mines about 100,000 tonnes of ore and 32,000 tonnes of waste rock per day, for a stripping ratio of 0.32-to-1. Ore, which grades 39% iron, on average, comes from five pits. Three pits — the Humphrey Main, South and West pits — send ore to the No. 3 loading pocket and ore hauled from two pits — the Humphrey North and Lorraine pits — goes to the No. 4 pocket. These pockets are large, 18,000-tonne and 60,000-tonne-capacity (respectively) underground storage bins, excavated in the waste rock of the huge, anticlinal structures that host the iron ore. An automated train haulage system, built in the 1950s, enters an adit in the anticline, which then splits to gain access to the ore chutes beneath the two loading pockets.

Blending is the key quality control factor in the mine. Ore is blended at the face according to three variables: iron content, magnetite content and iron recovery. By having five or six shovels mucking in either high- (greater than 20% magnetite), medium- (between 12% and 20% magnetite) or low-magnetite (less than 12%) areas, each ore-laden train bound for the concentrator has a magnetite quality of about 12% to 18%. In general, 70% of the iron in the ore occurs as hematite and 30% as magnetite. But some pits can be as low as 10% magnetite. Finding enough low-magnetite ore is the challenge for grade control specialist Clayton Dumaresque. There are more high- and medium-magnetite mining areas than there are low-magnetite areas.

To help ease that problem a bit, the company plans to develop a whole new pit, to be called the Spooks Pit, situated close to the No. 4 loading pocket, said senior geologist Thiagara Balakrishnan. The deposit is one of four within range of existing loading pockets which are suited to the company’s mining criterion. It contains about 80 million tonnes of low-magnetite ore and will be drilled off at every 50 metres along sections spaced 100 metres apart. Two other potential mining areas are the Sherwood and Luce areas. The company has about one billion tonnes of proven, probable and possible reserves in the Lab City area — good for 50 or 60 years of mining at present rates.

Computerized Truck Distpatch

One of the clearest indications that IOC is entering the 1990s with advanced open pit mining technology is the solar panels on six “signposts” situated throughout the pit area. Used to power isolated transmitter/receivers, they are part of a mine-wide, truck-dispatching system installed by Modular Mining Systems of Tuscon, Ariz., in 1985. The system automatically allocates each of 22 trucks operating on a given day to a particular shovel and tells the driver, via an on-board screen, where to haul the load. Ray Mason, superintendent of mine operations explains that, on average, each driver can expect to take anywhere from 20 to 25 loads from one of three shovels to either the 10×12-metre opening over a loading pocket or to the waste dump during a 12-hour shift. Shovel operators typically load 46 to 110 trucks in a shift. The mine operates seven days a week, 365 days a year and requires four dispatch operators in all (working one at a time). A shovel can load five or six bucketloads on to a truck within three minutes. One-way haulage requires 20 minutes on average.

One of the toughest things about operating an open pit mine in the harsh Labrador climate is the speed with which one must react to pump malfunctions. Once a pump fails, the lines have to be drained to prevent damage due to freezing. This problem would seem to have a simple solution in the form of remote monitoring of pump performance, but IOC has yet to come across a reliable monitoring system. Several have been tested, Mason says, but none has stood up to the rigors of a Labrador winter. As it stands, one man must travel to all the pumping points to ensure pumps are operating properly.

New Drills, Shovels and Trucks

Open pit mine equipment has changed significantly in recent years. Equipment has become so much bigger and faster that IOC can now justify significant new purchases. One new Bucyrus-Erie 295-B electric shovel was expected to arrive in December. It was to be operating by March. Depending on which direction the steel market takes, this buying pace could be maintained for the next two or three years, although no commitments have been made yet.

“The cost of maintaining the existing 12-to-20-year-old 2300 P&H and 280 B shovels is simply too high,” said Fred Ruegg, superintendent of field maintenance. “By purchasing new shovels, the company can cut operating and maintenance costs in half.”

Since the availability of the new machines will be higher, a smaller fleet will be required to produce the same amount of ore. The way it works now, if two machines are operating in tandem (one in high-magnetite and one in low-magnetite ore), and one goes down, then the other machine goes down to maintain the blend.

“For this reason, it’s important to have the machines running when you need them,” Ruegg said. IOC’s field maintenance department, which employs 100 people, rebuilds one or two car bodies on its small shovels every year.

Several unique design features will be incorporated into the new machines. The boom angle of the new shovels will be lower than the existing machines. That will be done to keep the truck away from the shovel during loading. Other changes required for IOC’s unique operating conditions include a 14-cubic-metre bucket even though the machine is designed to handle a 15-cubic-metre bucket. (Ore weighs 3.588 tonnes per cubic metre, waste 2.79.) Interior design changes to the operator’s cab include air conditioning for the hot Labrador summers.

Also on IOC’s Milwaukee shopping list are new 49-R electric blasthole drills, also from Bucyrus-Erie. Existing drills are only available for use 69% of the time, and the extra 16% availability expected from the new drills should allow operators a little more flexibility in their mine planning. We saw the gear box on one old drill being changed by maintenance crews during our tour. This, says Ruegg, is the most common component failure on the machines. The new drills, the first of which is expected in the first quarter of 1990, feature hydrostatic drives rather than chain drives and propel transmissions. Other features include an automatic levelling system, and a new electric pull down system eliminates feed chains.

The company is already well into a major shopping binge for new trucks. Ten 200-tonne Titans were purchased from Marathon Letourneau of Longview, Tex., beginning in June, 1989. They are part of a replacement program which was justified on the basis of potential savings in maintenance costs. The new haulers will replace a fleet of fourteen 150-tonne trucks. Ioc had not bought a new truck since 1981. Marathon even agreed to ship, at no cost to IOC, a spare truck to meet strict availability guarantees. Superintendent of Mobile Equipment Maintenance Philip Alport showed us a truck being erected in the company’s huge No. 2 garage.

“We sacrificed the advantages of having one crew assemble all the trucks in favor of a plan to have all our maintenance crews assemble at least one truck,” Alport said. “That way, they’d all be familiar with the vehicles. One experienced crew could have put one of the machines together in 10 days. It took about two weeks, on average, to erect each truck.

IOC has discovered that unlike market prices, maintenance costs can be controlled. So it is introducing a trouble-shooting system of maintenance. “We’ve started a system whereby we perform a tune-up on every machine every two weeks, religiously,” Ruegg said. “This way, we avoid breakdowns and increase availabilities. Nobody schedules maintenance like we do, guaranteed.”

By monitoring equipment failures and repairs 90% of the time, a computer can help determine the cause of future malfunctions. Ioc plans to take advantage of this by introducing a new computerized maintenance system marketed by Shaware of Burlington, Ont. It would integrate work orders with work history and parts inventory. Instead of truck service schedules being drawn up manually, for example, the computer will do it automatically. The new system is very detailed and complex; it will take about one and a half to two years to get it running according to specifications. A similar system is used at the Key Lake mine in northern Saskatchewan. Maintenance crews now routinely monitor vibrations on all high-speed motors for clues as to when a bearing needs lubricating, for example. Field maintenance accounts for about 12% of IOC’s mining costs.

Reducing wear on haulage truck boxes is one way savings have been made already. The wear bars on the new trucks are made of impact- resistant steel in the centre of the box and of wear-resistant steel on the front and sides of the box.

“We’ve also played around with the spacing between the bars,” Alport says. “If they are too far apart, the fines don’t fill in the gaps, so you don’t get that cushioning effect.”

Ioc uses emulsion explosives from two suppliers (ICI Explosives International and Salt Lake City, Utah-based Mining Services International, both of which have mixing plants in Labrador City).

Wall rocks are very competent and there have been no problems with wall stability.

Dry versus Wet Milling

Recoveries in IOC’s concentrator are running about 70%, but the company would like to get up in the 80% range. “Pilot plant work is required before we know whether we can do it,” said Chief Metallurgist George Chung.

Run-of-mine ore is hauled in 95-tonne, side-dumping rail cars 11.25 km to two Allis-Chalmers 1.52×2.26-metre gyratory cone crushers, adjacent to the concentrator. A travelling feeder distributes the minus-15-cm ore over 20 chutes in the 380,000-tonne ore storage building. Theoretically, some blending takes place here as well. Regardless, the ore is then fed into one of either two wet mills or two dry mills.

In 1986, IOC installed two 9.9-metre-diameter Dominion wet mills, replacing eight original, dry, autogenous Aerofall mills. Today, the company still operates two remaining dry mills, but only when necessary. Each wet mill can treat 1,550 tonnes per hour at a cost significantly lower than that of the dry mills, which require bunker C oil to remove all moisture from the ore. The wet mill performance is better, incidentally, than the 1,250 tonnes per hour originally anticipated. Energy consumption is slightly better, too, Chung said. Each mill is powered by two 2,600-kw motors and the original estimates called for 3.2 kw hours per tonne of ore treated. In 1989, power consumption averaged 3.1. Depending on feed, power consumption swings from a low of 2.0 kw hours per tonne up to 4.5. At 4.2 kw hours per tonne, the wet mills can process 1,300 tonnes per hour. The dry mills, in contrast, can handle 1,600 tonnes per hour.

Each dry mill is equipped with two 116-gigajoule burners, which are fueled by bunker C oil. They heat the air inside the mills to 870^o (deg)/C. A large fan draws the dried ore through the mill. Large ore particles stay in the mill and fines are swept out by the flow of air into a vertical classifier. The direction of the air flow takes a 90^o (deg) turn in the classifier, thus reducing the velocity and causing particles to drop out.

An expert system developed by Control International of Utah was installed on one of the wet mills in March, 1988. Since then, the system has achieved a 3% improvement during times when the wet mills are power-limited, which is 25% of the time.

Over the past three years of wet mill operation, IOC has found that grinding media are not required. With this out of the way, the company shopped around for mill liners and came up with some fantastic results from new liners. Operating hours range from 4,000 to 7,000, resulting in a 34% reduction in liner cost. Details were presented at a symposium on semi-autogenous/autogenous grinding sponsored by the Canadian Institute of Mining and Metallurgy in Vancouver in September, 1989.

“One third of our grinding is more expensive than the rest and we have to be conscious of reducing that cost,” said Concentrator Manager Tom Donnelly.

If Bunker C oil costs were to rise, for example, IOC could justify eliminating one or both of the remaining dry mills, he said. The cost of a single replacement should total $14 million and could be accomplished “on the run.”

IOC draws electrical power, at 46,000 volts, from the Churchill Falls generating station.

Spirals Important

Downstream of the grinding stage, capacity of the processing plant is limited to 2,000 tonnes per day. Two gravity stages and one magnetic separation stage follow the grinding stage. The spiral plant is by far the most important stage. And if there is a bottleneck in the concentrator, this is it.

Between 90% and 92% of all concentrates produced by the concentrator come from this part of the process. There are 30 lines and 200 Humphrey spirals per line for a total of 6,000 spirals. Installed in 1962, each spiral has a 34.3-cm pitch and five turns. Some patching has been necessary after 27 years of operation. The company had about 1,200 spare spirals to replace old ones. Ten lines are dedicated to one wet mill, six are dedicated to the other wet mill, 10 are dedicated to the dry mills and four are “swing” lines (i.e. operators can feed material from either the other wet mill or dry mill). At 43% iron, feed grades from the wet mills are higher than from the dry mills because of the classification system. Iron grades from the dry mills average 41% iron. The spirals classify in three stages: rougher, cleaner and recleaner. The tails from the first spiral stage are the final tails.

Cones for Fines

Eighteen Reichert cones handle a slightly finer feed. This circuit was designed and built in 1977 to handle 1,000 tonnes of feed per hour, averaging 40% solids and 32% iron. There are nine 4DS cones in the rougher stage, six 2DSSDS cones in the cleaner stage and three 4 DS cones in the scavenger stage. Each is two metres in diameter and has a deslime cyclone to raise the density, making for a total of 96 cyclones 25.4 cm in diameter.

With so much emphasis on gravity separation, water is a prime consideration in the IOC concentrator. It uses about 340,000 to 380,000 litres of water per minute. Some is reclaimed, but 110,000 to 150,000 litres per minute is “new” water from nearby Wabush Lake, the same lake where tailings are dumped.

“Garbage Can”

The magnetic separator is the “garbage can” of the plant. It was built in 1965 to treat the reject material from the cones and spirals. A second plant was built in 1973. The tails from spirals account for 90% to 95% of total feed to the magnetic separation plant. Feed grades run 21% to 23% iron. The feed is treated in five stages in low-intensity (0.075-0.08 Tesla), magnetic separators which are 1.8, 2.4 and three metres long. About 80% of the feed is rejected in the cobber stage. This material is reground in one of three 3.6×4.9-metre Allis Chalmer ball mills or one 5×8.5-metre Dominion ball mill. These reduce the feed to 75% minus 325 mesh to liberate the magnetite. This material does not go to the screens right away, but to a rougher magnetic separator first. Then the material is screened at 150 mesh, the undersize going to the finisher magnetic separator. The aim of the magnetic plant is to reclaim as much of the magnetite as possible. Only 1% to 2% of the magnetite is not recovered. The final products from the cones and the magnetic separator are pumped directly to the pellet plant. Recoveries in the magnetic separation circuit are about 60%. The final product grades about 90% magnetite and 68% iron.

Tails and Products

Ideally, the only tailings produced by the concentrator are the tailings from the magnetic separation stage. But in reality, when a spiral line goes down, for example, the plant dumps a stream to the tailings area in Wabush Lake. IOC is experimenting with various reseeding schemes to reduce the nuisance of dust from the tailings area.

Final products are de-watered before going to either the pellet plant or trains to be hauled to Sept-Iles. The moisture content of the product that goes to the pellet plant is 4.5% and IOC has the capability to reduce moisture contents to 2% for the 12-to-14-hour train ride to Sept-Iles. This is necessary to avoid freezing in the rail cars during the winter. Unlike many other mining operations in Canada’s sub-arctic region, the iron ore mines of Labrador City are serviced by rail lines from the south. This has kept the cost of transporting equipment to the site and iron ore products from the site less costly.

Low-silica Pellets

To the operators of the pellet plant, quality has another meaning. Here it means getting silica content as low as possible in preparation for expected higher demand by steel-makers for the low-silica variety. Silica content averages 4.75% now, but could go as low as 1.5%, said Superintendent of Operations Dave Pearcy. (Some customers, such as British Steel, prefer high-silica iron, averaging 5% silica.) “We want to have our act together within five years,” he said.

The pelletizing process begins with the regrinding of concentrator material to 66% minus-325 mesh. Despite the 13 regrind mills, this is the most serious bottleneck in the plant. Thickeners reduce moisture content to about 28% from 70%, then 36 disc filters dewater that material to 9% moisture. A binding agent is added to the filter cake concentrate. Ioc purchases 90,000 tonnes annually of a binding agent (bentonite clay) from Greece and other countries at a cost of about $200 per tonne. It adds about 0.45% silica to the pellets. The alternative is to go to a new technology — organic binders. That would involve 26 different addition points and 26 different mixers, one for each balling drum.

At 1,400 tonnes per hour, IOC’s pellet plant can annually produce more than 10.1 million tonnes of acid pellets. In recent years, a second production line has been added which produces two million tonnes of flux pellets per year. The pellets contain 12% dolomite and limestone.

Coke Breeze

To cut energy costs, IOC has started using coke breeze, purchased from Sault St. Marie, Ont., Cleveland, Ohio, and Chicago, Ill. The additive costs $7 million a year, but by using it the company is able to cut $17 million in annual Bunker C costs. But a regrind mill must grind the coke breeze, reducing the regrind capacity of the plant.

“We could go to 12 million tonnes per year if we had a separate small mill for the coke breeze, Pearcey said. “It would add stability and flexibility to the operation.”

The mixture is then run through one of 26 balling drums two to three times on average. These open-ended drums, which are three metres in diameter and nine metres long, are inclined at an angle of 7.5^o (deg).

“We would like to go to 3.6-metre-diameter drums lined with rubber,” Pearcey said. “This would eliminate the cutter bars and cut back on the weight of the machines. This in turn would increase the life of the bearings, which are the main cause of the unit’s malfunctioning.”

The material collects into balls which report to one of six travelling grate furnaces where temperatures reach 1,290^o (deg)/C. This process, called induration, drives off the carbon dioxide and other volatiles and cements the individual pellets.

About 80% of the pellets coming out of these furnaces are between 0.95 cm and 1.27 cm in diameter and have a compressive strength of 250 kg. This allows steel-makers to stack them in their steel furnaces. North American customers include Dofasco, Bethlehem Steel and National Steel. Ioc also has customers in Europe.

Pellets are shipped to Sept-Iles in one of four 265-car trains. The trip to tide water is downhill from an elevation of 540 metres above sea level.

No More Drill Sergeants

“We’re just now beginning to bring our maintenance back up to where it was (in the early 1980s),” Pearcey explained. “We didn’t cut back, we slashed back.

“Now we’re trying to get to the point where the supervisor is not a cop or a drill sergeant but a coach, trainer, motivator or facilitator.”

An example of this is an unsupervised team of unionized operators who have been using an IRD Mechanalysis predictive maintenance software package since March, 1989. They are using the computer to analyze vibration signals on all major production fans, gear boxes, pumps and ball mill pinions and motors in the pellet plant. The idea is to predict mechanical failure before it happens.

“One of the most important parts of making gains is motivating the people who are going to do it for us,” said Plant Manager Stephen Vessey. “The most successful corporate turnarounds in North America have involved companies that are strongly inclined toward drawing on the talents and strengths of their workers. IOC has not moved far enough in this direction.

“What we lacked was the ability to use the information, knowledge and skills of the people who are doing the work. When I look around at what these people do in the community when they go home at night, I’d say we have the potential to develop a much more participatory workforce, one that can contribute significantly more to our success. Technology is the small issue.”

STOP Milling

The chemical giant Du Pont holds the world record in industrial safety. Through a program called Safety Training Observation Program (STOP for short), this multi-national corporation has experienced a significant reduction in lost-time accidents in its plants worldwide. That is why Iron Ore Co. of Canada has chosen this program for its concentrator plant in Labrador City, Nfld.

“We have to be careful to incorporate all our people resources within the concept of quality control,” Concentrator Manager Tom Donnelly told The Northern Miner Magazine.

“What we want to avoid at any cost is being inexperienced in matters of safety. We’re being very up front about that.”

Every front-line supervisor in the concentrator has taken a 2-day course on managing safety.