Mine and Plant: Good morning, Manitoba!
Canada’s fourth largest copper and zinc producer, Hudson Bay Mining & Smelting Co., Limited (HBMS), is energizing its northern Manitoba facilities, extending their future to 2016 and beyond. At a cost of Cdn$400 million, the 777 project represents the largest single investment in the company’s 75-year history.
While HBMS was incorporated in 1927, the Flin Flon zinc-copper orebody had been discovered in 1915. The orebody was first exploited as an open pit and then underground via two mine shafts, north (1935) and south (1939) of the deposit. The Flin Flon mine operated through 1988, and was in fact the company-maker for HBMS. A metallurgical complex was constructed in Flin Flon (on the Manitoba/Saskatchewan border) in 1929, and has worked around the clock since it started up in 1930, with only two short interruptions.
To the end of 2001, the company had operated 29 separate mines in northern Manitoba and Saskatchewan, mining 142 million tonnes of ore to produce 3 million tonnes of copper, 5.2 million tonnes of zinc, 8 million ounces of gold and 116 million ounces of silver.
Companies associated with the Anglo American group have held a substantial interest in HBMS since 1962, increasing to 100% interest in 1983. HBMS today is a wholly-owned private company, part of the base metals division of Anglo American plc., which is headquartered in London, U.K.
By 1995, rising costs and falling metals prices had placed the company in serious financial difficulties. The all-in zinc production cost was US$0.74 per pound when the LME price of zinc was around US$0.47. The lost-time accident frequency rate in 1994 had been 16.2 per 200,000 man-hours worked.
After significant operational and safety improvements between 1996 and 1998, a decision was taken in 1999 to go ahead with a six-tier project called “the 777 project”. This followed a groundbreaking “Amending Agreement” ratified in March 1998 by HBMS’s nine unions in Flin Flon, providing for labour stability through 2012.
The 777 project would result in two new mines, an environmentally updated copper smelter capable of meeting voluntary environmental commitments, expansion of the Flin Flon concentrator and the construction of a new technology electrolytic zinc cellhouse to substantially improve zinc throughput capability as well as introducing many productivity improvements. Two of the primary goals of the project were to significantly reduce the all-in cost of zinc produced and to continue to improve the lost-time accident frequency rate to a sustainable level below 1.0 per 200,000 man-hours worked. At project completion HBMS expects to be inside the lowest cost quartile of zinc producers worldwide, putting it in a highly competitive position.
Many parts of the 777 project are already complete. The Chisel North mine has been operational for some time, and was officially opened on June 1, 2001, together with the Snow Lake concentrator, which has been revamped to process the ore. An environmental project was successfully completed on the copper smelter and Flin Flon now enjoys significant atmospheric air quality improvements as well as a reduction in stack dust discharges. The pressure leach zinc plant, commissioned in 1993, was expanded by 15% and an efficient new zinc cellhouse was built using leading-edge technology, at a cost of over $100 million (see “New Zinc Cellhouse”). The expanded plant and cellhouse have been in full operation since July 2001. Many parts of the infrastructure, especially around the Flin Flon plant, have also been upgraded as a part of the 777 project.
While all six of the 777 sub-projects are not yet complete, the four complete ones have had an impact. In 2001 the all-in zinc production cost was down to US$0.69 per pound and the lost time accident rate was 0.7. Completion of the Flin Flon concentrator expansion during 2002 and the 777 mine, which starts limited production late in 2003, will further add to the gains.
Of the two jobs to finish, the largest project is construction of the 777 mine, a 52-month, $200-million expenditure, which is on schedule (see “New Mine Brings Long Life to Flin Flon”). The 777 mine is using innovative technology to sink a 1,530-m deep shaft from surface to access the deepest orebody ever mined in Flin Flon. Started in 1999, the mine should reach full production during 2004 providing 1 million tonnes per year of feed for the Flin Flon concentrator. The Flin Flon concentrator is being expanded 20% from 1.81 to 2.18 million tonnes of ore per year: this 36-month project is on schedule but not yet complete.
Presently, the company has five operating mines–the Callinan, Trout Lake and Konuto Lake mines, all in the Flin Flon region, the Chisel North mine near Snow Lake, which began commercial production in 2001, and the Ruttan Mine in Leaf Rapids (200 km northeast of Flin Flon) purchased by HBMS in 1987 from Sherritt Gordon Mines Ltd. Ruttan mine is slated to close in June 2002. The company has concentrators in Flin Flon, Snow Lake and Leaf Rapids, each of which can produce copper and zinc concentrates. The copper smelter, with an annual capacity of 90,000 tonnes of anode copper, and the hydrometallurgical zinc plant, with an annual capacity of 115,000 tonnes of cast zinc, are situated in Flin Flon.
Peter Jones is the new president and CEO of HBMS and has been onsite for seven years. He was formerly a consultant in Vancouver, mostly working with Cominco Ltd. He outlined the situation for CMJ last December. “Our employment has steadily decreased due to retirement and other incentives to leave, from about 2,300 people five years ago, to, in the order of 1,800 today. In Flin Flon there have been no layoffs of long-term employees. There will be about 1,450 people remaining on HBMS’s rolls at the end of June 2002 after the Ruttan mine closure.”
New mine brings long life to Flin Flon
A decade ago, HBMS’s northern Manitoba mines were expected to run out of ore by, at the latest, 2004. In a measure to extend the life of the mining camp, the company conducted a massive exploration program starting around 1996 using both Anglo American’s Spectrum airborne electromagnetic system and deep drilling along the Flin Flon greenstone belt, one of the most productive greenstone belts in Canada for copper/zinc volcanic massive sulphide deposits. The geophysics pinpointed 1,300 anomalies for follow-up.
The Spectrem system has been credited with discovering two new mines, the Photo Lake mine in Snow Lake and the Konuto Lake mine. The deep drilling program, which also tested previously undrilled areas in the core of the mining camp, late in 1993, intersected significant mineralization at the 777.
Intense follow-up drilling from surface and underground outlined an orebody–dubbed “the 777”–consisting of two massive sulphide lenses overlying each other and associated stringer mineralization. The lenses, above a thick package of rhyolites, have a strike length of 300 m, and are known to extend from 900 m to 1,500 m depth, with a dip of 41* to 45*. Mineable reserves and resources to date total 14.5 million tonnes grading 4.56% Zn, 2.5% Cu, 2.1 g/tonne Au and 29.83 g/tonne Ag. Ironically, the deposit lies in the heart of the camp right below the town of Flin Flon, and may be associated with the Callinan deposit and the original Flin Flon deposit but at substantially greater depth.
MRDI (now AMEC) of Vancouver began a feasibility study for the 777 mine in late 1998, including the shaft, headframe, hoist house, office/dry, ventilation and site preparation. AMEC began the basic engineering in April 1999, with its subconsultants, G.L. Tiley & Associates of Flamborough, Ont., and Anglo American Technical Services (AATS) of South Africa. The development was given the green light in September of 1999.
McIntosh Engineering of North Bay, Ont., is doing the detailed engineering for the underground development and infrastructure while AMEC is engineering the 777 mine paste-fill system.
The shaft was collared in an already-disturbed area; preparation included removing more than 100,000 tonnes of
accumulated zinc residues. The site was prepared and the surface structures, including a steel headframe, completed by the beginning of 2000.
JS Redpath Limited began shaft-sinking in June 2000, and is expected to reach the final depth of 1,530 m by mid-July 2002. The lateral development should be complete a year later. First production will be late in 2003, and the mine will be in full production by August 2004. In the future the shaft has the capability of being deepened to 2,000 m.
The development and construction phase of the 777 mine will require up to 150 contractors and HBMS employees. Once completed, the 777 mine will employ up to 250 operating personnel.
The 777 mine circular concrete shaft has an inside diameter of 6.7 m. The wall has a nominal concrete thickness of 15 cm, but it runs up to a width necessary to bond with the actual shaft excavation.
Two Hepburn double-drum hoists were brought to the 777 mine from the Stanleigh mine in Elliot Lake, Ont. The 1,300-kW hoist is for service, employing a double-deck personnel/materials cage with a counter weight; this can transport anything up to half a 50-tonne truck. The production hoist is a 4,100-kW unit that runs two 18-tonne skips, which travel up to 850 m/minute. A third hoist is a single-drum ABB, purchased second-hand but unused from Nevada, that runs a double-deck, 12-person Mary-Anne service cage.
The two double-drum hoists were installed before shaft-sinking was started, and used for the sinking process as well as emergency escape during sinking. This approach lessens the down time of the switch from shaft-sinking to shaft production. The hoists use the Modicon system of automation: a Tiley brake regulator to control emergency braking, and a Tiley hoist supervisor.
The service lines in the shaft include 20-cm air, 10-cm water, 10-cm drain and 10-cm spare. As well, there is a temporary 1.37-m-diameter ventilation duct; the shaft will eventually be the fresh air intake for the mine with two axivane fans at surface with propane air heaters. The centrifugal exhaust fan also on surface has been relocated from White Pine Copper in the United States. Two 20-cm drain lines will be used for draining the mine through two high-pressure pump stations adjacent to the shaft.
Jack Ayotte is HBMS’s 777 mine construction superintendent, and Chris Hatherly is in charge of the Redpath sinking team. They explained how the shaft-sinking is done, as we traveled down the shaft to the excavation for the 1262 level station.
All the work takes place from a platform (galloway stage) that is lowered 6 m after each full faced round is blasted from the bottom of the shaft. On the platform are four 6.4-m jumbo drills, and two clams to muck into the bucket. There are two sinking buckets in counterbalance, which are used to move personnel, muck and materials. A steel cover above the bucket protects personnel in the buckets from falling objects, and each bucket is guided by two ropes. “The crews are drilling 6-m rounds, which is extraordinary,” says Jones. “This is the first time it has been done for a complete shaft. Our contractor Redpath are doing it faster and cheaper, pushing the envelope.”
The cycle is drill, blast, muck, wash, bolt and concrete. A 20-cm centre hole is drilled using a dedicated drill together with a pattern of 5-cm holes around it to break the rock successively into the centre. 28-Mpa concrete is used with a non-chlorine accelerator to help it set quickly. Every lift contains all the services in 6-m lengths–including fresh air vent ducting and pipes. The crews have been cycling approximately every 30 hours.
The lateral development will be done from four primary level stations–the 1,082 m, 1,262 m, 1,412 m and 1,465 m. The crusher station is located at 1,465 m and the main loadout station at 1,508 m. In total, there are eight stations over the entire 1,530 m of the shaft. Underground will be a 122-cm x 152-cm jaw crusher. Crushed ore is sent to an 1,800-tonne fine ore bin, and then to a conveyor that feeds the skip loading pockets. On surface the ore is dumped into a 1,400-tonne ore bin. The skips will initially handle 2,750 tonnes of ore and 1,100 tonnes of waste every 24 hours, and will be able to hoist well in excess of this tonnage without being modified.
Says 777 mine project manager Pat Smyth: “We are developing the stations as we sink and driving the large ones to a waste pass to facilitate development once the shaft is complete.
“We have had an extremely good safety record,” he continues. “Currently we are over 500 days without a lost time accident.” The good record is because HBMS, Redpath and all our contractors work hard on safety programs. We work hard at the basics of safety –keep everything clean and orderly; spend lots of time going through the procedures. Redpath has always been strong on safety. We have reached the stage where we have steady crews who know each other and the routine is well-established.”
As part of its efforts to reduce operating costs, HBMS is in the process of standardizing its equipment. The company has partnered with Atlas Copco, which is providing underground Rocket Boomer jumbos for all the Flin Flon mines and 40-tonne Wagner mine trucks and 7-yd Scooptrams at Chisel North and Konuto Lake mines. To provide product service in Flin Flon and Snow Lake, Atlas Copco has in turn opened a warehouse and service centre in Flin Flon.
In production, the 777 trackless mine will use typical large mobile equipment underground, so it will need to be well-ventilated. Ore extraction primarily will be by modified mechanized cut-and-fill mining; other portions will be longhole stoped with close sublevel intervals. There will be paste backfill throughout, with the paste transported underground via a borehole. The paste backfill will be made within the Flin Flon concentrator from partially classified tailings and from there will go straight underground.
The development waste rock is being segregated into acid-generating and non-acid-generating stockpiles. The acid-generating waste is safely disposed of in the HBMS tailings dam area. Following closure of the mine, the site will be left in maintenance-free condition, with no continuing significant environmental impacts.
Making the Metals
“Fundamentally we produce in excess of 115,000 tonnes of cast zinc per year and about 90,000 tonnes of copper as anode,” says Peter Jones. “Most of the potential profit comes from the zinc side depending on metal prices. Almost all the zinc that we process is from our domestic mines, but we purchase 30-40% of our copper concentrate to fill the smelter’s capacity. We also produce about 70,000 ounces of gold and 1,000,000 ounces of silver per year, which forms in the order of 10% of our revenue.”
The zinc hydrometallurgical plant uses proprietary Dynatec two-stage pressure leaching technology, installed in 1993, with three autoclaves to produce a zinc-rich solution. The solution is purified and then sent to the electrolytic cellhouse that produces zinc cathode sheets. These are sent to the casting plant for melting and casting into various shapes and alloys suitable for sale. The most recent upgrade and expansion, in 2000, modified the purification circuit, replaced the 1930s tankhouse, and increased zinc capacity of the entire plant by 15% including the oxygen plant. Two Filter Phillipe belt filters were also installed in the pressure leach facility to improve zinc recovery from plant tailings.
The copper side is a fully pyrometallurgical process; much of the plant is the same configuration as when constructed in 1929. Copper concentrate is roasted and then sent to the reverb furnace where it is melted to form matte. This goes to one of three converters, from which the copper is sent to one of two anode furnaces. The copper is poured into an anode casting wheel. The anodes are refined into cathode copper at a separate location.
In 1995, an 80% reduction in stack particulate emissions was achieved by installing Gore-Tex bags in the smelter bag-house. The bag-house was replaced in 2000 by an electrostatic precipitator, as part of the
smelter gas-handling project. The net result was a reduction of 90% in fugitive gas emissions at ground level and compliance with voluntary dust emission levels, which represented a reduction of 62% from 1988 levels.
New Zinc Cellhouse
Peter Jones describes some interesting aspects of the project. “For the zinc plant expansion, we used Asturiana de Zinc proprietary technology from Spain. This is its first use outside of Spain. The cathodes are 3.6 m2, the largest anywhere in the world and the most efficient. The new cellhouse is practically automatic, with a small number of operators who monitor functions. We believe this is the best available technology.”
CMJ toured the new cellhouse and the casting plant with technical advisor Mark Watling who said, “The $100-million-plus zinc electrolytic cellhouse and purification improvements, replace the tankhouse built in 1930, and were designed using the most modern zinc electrolytic plant technology anywhere in the world.”
He also said, “There are two rows of 35 cells each. In each cell are 110 aluminum cathode starter sheets and 111 anodes. The current used to electroplate is 473 A/m2. The anodes contain lead and 0.46% silver. The cathodes have a 5-6-year life, and the anodes will last eight years. Half the cathodes from each cell are alternatively stripped every 48 hours. The cells and anodes are cleaned every 23 days.”
The cellhouse has already exceeded its specified production rate. It has been constructed with a provision to add more electrodes to the cells at a later date; this could boost cathode production by another 15%.
Two automatic cranes transport the cathodes, positioning them exactly, within 2 mm, eliminating much of the former manual labour. The sound of music is heard whenever the overhead crane moves, to warn people of the movement, and there is a large range of music available.
The big cost reduction comes from the reduction of personnel from 90 to 26 in the new cellhouse as well as from energy use reduction. The cellhouse accounts for half the company’s $26-million power bill each year. The new cellhouse has improved the use of electricity per tonne of zinc produced by about 18% compared to the old process. Intake air, at a rate of 13,580 m3/ minute, is heated by propane and circulated in the cellhouse. The ventilation system makes respiratory protection unnecessary in the normal working locations and travel ways. Ventilating air is blown through four propane heaters by centrifugal fans in the basement. It passes through slots in the floor to the working level and then passes over the cells before exhausting through the four roof-mounted cooling towers. The cooling towers are dual purpose: they are used to cool the electrolyte and maintain it in the optimum range of 32* to 38*C, and also to draw the air through the cellhouse in combination with the basement air intake units.
All of the zinc product is cast in the ISO 9002-certified casting facility. It produces 1-tonne jumbos and long blocks and 25.6-kg slabs in three separate casting lines. The plant produces special high-grade zinc, and HBMS supplies its customers with products that are well within specification including zinc alloyed with aluminum.