Operations: New Lease on Life for Thompson Operation
Inco’s Thompson operation has been in production since 1961, with nickel-cobalt mines, as well as a mill, smelter and refinery. Its underground mines and pits lie along the Thompson Nickel Belt in the north-central part of the province.
The ore is characterized by relatively high nickel grades (2.5% Ni) and cobalt content, but low amounts of copper and platinum group elements. Today the mine draws ore from the Thompson mine (T-1, T-3 and 1-D orebodies) as well as the Birchtree mine. CMJ visited Thompson in December 2001.
The Thompson operation produced just less than 113 million pounds of nickel–about 1.2 million pounds over plan–in 2001, with byproduct cobalt. The operation has a young management team under General Manager Joe Loring, and a relatively young workforce of approximately 1,400 people.
Birchtree Deepening Project
The Birchtree underground mine is one of Thompson’s older, lower grade mines, but the current deepening project is turning it into the future of the operation. Birchtree began production in 1966, but by 1997 the mine was experiencing high costs as it was running out of shallow ore.
Inco held open a door of opportunity for Birchtree. The mine’s 76 employees continued to operate the mine while a “co-design” team of six (later seven) of its salaried and hourly employees was asked to find a way for the mine to become breakeven at an LME nickel price of $1.80/pound. This would require a bottom line direct mining cost of Cdn$26 per ton of ore.
Pat Babulic, who was then the Birchtree mine superintendent, chaired the co-design team. Its charter allowed them to make any changes, as long as they stayed within the mining laws and the collective agreement and operated safely. The team proposed going to a 12-month operation, making organizational changes without layoffs and changing to central blasting procedures. They also moved forward with improving the handling and placement of rockfill, equipment availability, and upgrading equipment including replacement of a 9-yd3 scoop with a lower-cost 7.5-yd3 unit.
The recommendations were accepted at the end of 1998. Within two months, Birchtree boosted production by 20%, exceeding its target ore level of 1,800 tons/day at a cost of only $23.06 per ton, a drop of more than 25%. Productivity soared from 17 tons/hourly manshift in 1996 to 33 tons/hourly manshift in 1999. And at the same time, Birchtree mine operations went without a disabling injury for 15 months.
The underlying purpose was to create a financially attractive project with a credible business case that would convince Inco’s head office that Birchtree could profitably expand downward into the ore that would spell the future for the operation. A key component of the revised plan was to boost production from 1,800 to 3,500 tons/day. “The operation was pretty lean before,” says Babulic, who is now project manager of the deepening, “but we would gain economies of scale.” In the future, they will add one shift underground to move to a four-shift operation (168 hours/week.)
The deep ore occurs within the 108 and 84 orebodies, which lie between the 2,300- and 4,000-ft levels.
The project would involve additional engineering, surface and underground ventilation upgrades, extension of the ore-waste pass system, construction of a deep loading pocket, skip changeover, upgrading the backfill system, and installing a new crusher on the 4000 level. The mine would be developed in two portions, from 2,300 to 2,750 ft, and from 3,400 to 3,922 ft. (The section from 2,750 to 3,400 ft would be developed at a later date to maintain production.)
The corporation accepted the proposal for the three-year, Cdn$70.4-million project in mid-February 2000, and engineering work began immediately. Because of an earlier, aborted deepening project, the shaft was already at 4,200 feet, and the cage was tied in to the full depth.[continued on page 44]
The mining contractor was mobilized in mid-April 2000. Early work centred around establishment of a ventilation circuit to allow development to proceed on the lower levels. Work on these levels (3450, 3922 and 4050) began approximately one month later and was focused on getting the new muck-handling facilities excavated and constructed. About 3,000 feet of new raises were driven to extend the ore and waste passes from 2750 level to the new loading pocket located on 4050 level. The new loading pocket sees ore and waste being fed from bins between 3922 and 4050 to the hoppers via a conveyor. The entire system from the ore/waste bins to the skip dump is linked and controlled via PLC.
Surface upgrades were made to fresh and return air systems. This included extension of the surface power distribution and installation of new fan houses. The fresh air facility, including the propane power heating plant, was completed by November 2000. Two new horizontal 8-ft diameter fans operating off 1,500-hp motors drive the systems. To support this underground, new fresh and return raises are being driven from 2750 to 3922 levels and the return system is being twinned from 2300 level to surface. These changes will allow ventilation capacity to increase by 53% to 635,000 cfm. To date, 5800 feet of ventilation raises have been driven completing the fresh air system. This leaves 2600 feet of return air raise to be driven.
In January 2001, work began on the critical process of changing over from the old to new skip hoisting system. The old system loaded skips at the 2460 level and the new at the 4050 level. The 25-year-old pentice, a protective barrier between existing skip compartment and deepened portion below, was removed and 400 feet of shaft was re-timbered. This allowed for the existing 10-ton bottom-dump skips to be removed and replaced with 12-ton front-dump skips. The changeover to front dump skips required skip dump modification including scroll removal. Brakes also had to be upgraded because of larger payloads and greater depth. Once the new 12-ton front-loading skips were installed and banked, new hoist ropes were installed on the Keope hoist. The new skips began to hoist development ore in early March 2001.
Alex MacIntyre and Associates will continue with development until the end of 2002. At this point, development will be at the stage where production can be sustained on two fronts – one above 2750 (until 2010) and the other working up from 3922 level. Future development will involve connection of these two areas by a ramp from 3450 to 2750 levels. This will permit production from this zone to be maintained until 2014. Farther down the road, 2009-2014 will see development and production of the 108 orebody.
The current backfill system involves pumping slurry from the mixing plant on surface and trucking the mixed backfill to the stopes. This causes problems in workplace conditions because the line from surface to underground creates large flushes that introduce cement into the downstream de-watering system. In addition, the slurry slops out of open trucks and ruins roadbeds. To eliminate these problems, Birchtree is moving to a new rockfill system where dry binder (30% portland and 70% flyash) is moved pneumatically from surface to the dump point. There it will be batched in a colloidal mixer and applied to the rockfill. Both systems operate in parallel at the moment, although the old system will eventually be phased out.
Sixteen thousand feet of drifts, ramps and raises were excavated between 2750 and 2300 levels to produce early ore in the last quarter of 2001 from the upper orebody. In fact, 30% of the hoist came from the deepening in November 2001. At full production by the end of 2003, Birchtree will provide half the operation’s ore. By then, the operations and maintenance workforce should number about 100, with the extra people probably drawn from the Thompson mine as its production decreases.
Superior Quality Product
The surface operations include a mill, a smelter and nickel refinery that on average make 112 million pounds of nickel per year in the form of R-ROUNDS* and S-ROUNDS* as well as nickel cathode sheets.
Thompson’s cob
alt oxide is processed at Clydach for customers and its cobalt hydrate is refined at Port Colborne. The Thompson operation is Inco’s only operating unit that makes electrolytic nickel.
The product is 99.9% pure nickel. This is important because Inco customers’ electroplating processes require electrolytic nickel that is almost free of contaminants such as lead or zinc. Such contaminants would go right through their processes and end up in their final products. In 2001, 98.5% of the nickel cathode and 100% of the ROUNDS product produced at Thompson operation were sold as marketable products. This high quality product commands a higher price than the LME price. Production, marketing and distribution of electrolytic nickel are registered to the ISO 9002 standard.
Refinery superintendent Lovro Paulic showed CMJ around the refinery. “There have been significant improvements in the purification process over the last 40 years,” says Paulic. “In the Tankhouse area, new cathode boxes and straightening techniques are currently being tested to improve the quality of the product and the ergonomics of producing the product.”
The anodes arriving from the smelter contain 75% Ni, and are submerged between the cathodes in each of the 684 plating cells. A total of 9,250 amps of direct current dissolves nickel from the anode. At the same time, nickel is plated onto the cathode sheet. About 65% of the anode dissolves, leaving behind slimes, which are collected and returned to the smelter. “If we were building the refinery today,” says Paulic, “we would probably make dimensionally stable anodes that don’t dissolve.”
The nickel-laden electrolyte (anolyte) is pumped to the purifying system, which removes most contaminants. The purified electrolyte then returns to the tanks for plating. It takes one day to grow a starter sheet, five days to grow the R- or S-ROUNDS and 10 days to grow a full cathode slab in the tanks. The cathode slabs are grown thicker than most–at least 13 mm thick. The slabs are sheared into plating strips or sent to Port Colborne to be cut into 2.5-cm squares. ROUNDS grow on openings on the painted surface of permanent cathode sheets, a process developed at the Port Colborne refinery.
Inco’s Thompson operations are licensed to emit 220 kilotonnes of sulphur dioxide annually. The company stays within these limits in accordance with provincial regulations. Inco emissions at Thompson are 50% less than they were 15 years ago. This has been achieved by rejecting as much sulphur-containing pyrrhotite as possible before it reaches the smelter. In terms of day-to-day operations, Inco constantly monitors SO2 emissions and cuts back smelter operations through its Voluntary Emissions Reduction Program (VERP). In January 2002, the Thompson operations established a community-based Public Liaison Committee that will meet each quarter to discuss environmental concerns the community might have about Inco’s Thompson operations.
Increasing Purchased Feed
Even with the Birchtree expansion, there is not enough local ore to keep the smelter and refinery working at capacity, so the operation has increased its purchase of outside feed.
The Thompson smelter has been accepting small amounts of outside nickel concentrates since the early 1980s. By far the most significant amount of outside feed is coming now from the Cosmos open pit nickel mine in Western Australia, owned by Jubilee Mines. The Thompson operation has a three-year contract ending in 2004, to buy and ship all the Cosmos concentrate. This amounts annually to 55,000 tonnes grading 19%-20% Ni, with 23 million pounds of contained nickel.
The Cosmos concentrate has a bit cleaner gangue than Thompson’s own concentrate and metallurgically processes well through the roaster. If the Cosmos mine expands to include an underground mine, then Thompson will be in the running to receive its concentrate for another 3-3.5 years.
In 2001, outside feed (mainly from Cosmos) made up 16% of the new nickel feed that went into the smelter, and this will increase to 23% of the feed in 2002. The other outside feed, amounting to 4 million pounds of contained nickel, includes recycle streams from the Thompson operations as well as nickel sulphate from Sudbury. Thompson has also smelted a small quantity of recycled materials from multiple small sources.
The key advantage in taking in the Cosmos feed is so the smelter and refinery can work at capacity, lowering unit costs. Manitoba has a competitive advantage in that it has amongst North America’s lowest rates for electricity–3-cents/kWh regardless of the time of day. This is a strong reason for Inco to direct outside feeds to Thompson, since energy is a major cost factor in the operation. Admittedly, the drawback in purchasing outside feed is that the transportation costs (especially from Australia) can be substantial, cutting into the profitability compared with local material.
*Trademark of the Inco family of companies
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