|The new spread of TBG Contracting Limited included this twin ElRus 6 by 20 screen unit.
|Alberta’s oil sands deposits are worked using some of the world’s biggest mobile equipment. Rolly Boissonnault, Athabasca Minerals area manager, and the massive Terex MT 6300 AC haul truck.|
|Both of Stony Valley Contracting’s spreads utilised Metso Nordberg Omnicone 1560 cone crushers.|
mm minus finished product on one of Stony Valley Contracting’s spreads
was stockpiled by to a 38 m long Superior Pinnacle radial stacker.
|The Surmont Sand & Gravel Limited spread incorporated this Metso Nordberg 7 by 20 triple deck screen.
crusher feed belt on TBG Contracting’s new spread had a folding top
section to allow clear crusher access, one of a number of plant
features designed with increased safety and efficiency in mind.
|At the Surmont Sand & Gravel Limited spread, pit run was fed a jaw screener plant where a double deck Terex Cedarapids 6 by 16 screen was teamed with a 3647 Metso Nordberg C96 jaw crusher.|
KPI-JCI 900 mm by 46 m Superstacker on the Surmont Sand & Gravel
Limited spread stockpiles the first of many thousands of tonnes of 75
mm minus road base.
|The Kawasaki 115ZV wheel loader of Inspek Crushing, another contractor at Susan Lake.
Nolan adds that changes in raw material extraction and haul methods used by the oil sands companies have been significant drivers of increased aggregate demand. Originally, bucket wheel excavators discharged excavated bank material onto long field conveyors taking raw oil sands to processing plants. Later, most companies replaced bucket wheel excavators with draglines, but the overall effectiveness of the process was still dependent on the reliability of the conveyors.
In practice, it was found that conveyor breakdowns caused unacceptable delays in production flow and many companies made the transition to mobile equipment. Today, virtually all of Alberta’s oil sands deposits are excavated by face shovel and hauled by off road trucks, with economies of scale achieved through the use of some of the world’s biggest mobile equipment.
Susan Lake’s impressive customer list includes Syncrude, Shell Canada Energy, Petro-Canada, the Canadian Natural Resources Limited Horizon project, as well as Lafarge, Inland Concrete, Burnco Rock Products and a number of Fort McMurray construction companies. Equally impressive is the list of applications for Susan Lake’s products. Kirk Farrell, mine engineer with Shell Canada Energy, explains some of the oil sands applications: “Our oil sands deposit is dynamic and requires huge volumes of fill and road base material for the ramps and haul roads used by the heavy haulers. Pit run is also used in the construction of maintenance pads, while oversize from Susan Lake is used as rip rap to control erosion in tailings ponds and drainage systems. At the other end of the size scale, a naturally occurring grey sand in the deposit known as Pleistocene fluvial sand contains almost no fines and is ideal filter sand in dyke and chimney drain applications.”
About 45 million tonnes of aggregate have been removed from the Susan Lake pit since operations commenced in 1998. Athabasca Minerals area manager Rolly Boissonnault explains that the Susan Lake pit extends some 3,750 hectares (9,260 acres), with the current development area covering about 485 hectares (1,200 acres). Ultimately, the Susan Lake pit will itself become part of the oils sands operations, as the aggregate deposit sits immediately above the Athabasca Oil Sands. Once the aggregates are extracted, the underlying oils sand will be extracted from the respective leases of Shell Canada Energy, Petro Canada and Syncrude.
Boissonnault adds that the aggregate deposit has up to 63 feet (19.2m) of usable material, with the top layer mostly used for pit run and granular base applications. Below the top layer and typically 3 m down, there is a layer of gravel up to 10 m thick suitable for asphalt or concrete aggregate applications. Below the gravel layer, there is a layer of sand some 4 m thick. Virtually all of the deposit is utilised with the exception of a 0.5 m cap layer that is left in place to keep the underlying oil sands sealed.
Stony Valley Contracting
At the time of Aggregates & Roadbuilding’s visit, several crushing contractors were in operation at the pit. One, Stony Valley Contracting, was operating three separate ElRus spreads including two dry crushing spreads and a sand screening plant. The first Stony Valley Contracting plant seen was producing 38 mm minus road crush (granular base) and sand byproduct at 300 tonnes/h from pit run containing individual pieces up 600 mm. At this plant, a Caterpillar 988H wheel loader charged a feed hopper equipped with a hydraulic lift grizzly set at 400 mm spacing to separate large boulders. Feed from the hopper was conveyed to the 4 by 8 screen of a jaw screener plant where part of the sand fraction was separated and stockpiled. At the same time, oversize passed through the unit’s 2030 jaw crusher, with jaw product going forward to a 6 by 20 triple deck screen. The screen separated finished product from material larger than 38 mm with oversize conveyed to a Metso Nordberg Omnicone 1560 cone crusher in closed circuit with the screen for further reduction.
Stony Valley Contracting’s second plant was producing 75 mm minus granular base as a single product. Here, the feed was first crushed by an ElRus 3042 jaw crusher and then separated by a 6 by 16 primary double deck screen. In this spread, oversize was crushed by a 2236 jaw crusher in the secondary position. From there, secondary jaw product was directed to a 6 by 20 triple deck secondary screen with oversize from this screen crushed by a Metso Nordberg Omnicone 1560 cone crusher in closed circuit. The 75 mm minus finished product off both primary and secondary screens was conveyed by a series of field conveyors to a 38 m long Superior Pinnacle radial stacker.
TBG Contracting Limited
TBG Contracting Limited, part of the Lafarge group, had two ElRus spreads in operation at the time. At the first plant seen, material already crushed to 102 mm minus was being processed into a single 20 mm minus product. This particular product will be used as wash plant feed but has the same specifications as granular road base. In operation, feed material from a 1.2 m wide belt feeder was conveyed to a new twin ElRus 6 by 20 screen unit. The primary screen’s upper deck was fitted with 38 mm screen cloths to spread the load onto the lower deck, fitted with both 19 mm and 22 mm opening screen cloths. Oversize from the primary screen was directed to the spread’s Sandvik CH660 cone crusher, a new unit that was being commissioned at the time and seeing its first hours in service. Material discharging from the CH660 was conveyed to the secondary screen for further product separation, with oversize also returned to the CH660. General foreman Don Polowy explained that product specifications include 60% crushed surfaces on two sides in the 20 mm by 10 mm size range. The product is made slightly coarse, as the fines content can increase by up to 3% during loading, rehandling, placement and compaction. Samples are typically taken every 1500 tonnes to check gradation.
Polowy also pointed out a number of plant features designed with increased safety and efficiency in mind. To facilitate set up, the new plant is equipped with 150 mm hydraulic jacks at both the front and rear, while heavy duty D rings welded into the frame provide strong chain attachment points to avoid frame bending during set up or take down. Polowy also noted the single pin design of the Martin Engineering QC #1 heavy duty belt cleaners which allows a fast, no tool blade change. In addition, motorised head pulleys on both 1.5 m wide cross conveyors simplify conveyor reversal and also eliminate any potential interference between conventional cross conveyor drives and the product take away conveyors. Also, conveyor tail pulley take up is achieved by a simple hydraulic system that utilises grease jacks to provide the necessary pressure. This design eliminates the need for wrenches to move the pulley as well as the time required to remove and reinstall any guarding. As an added safety bonus, the adjustment valve is mounted some distance from the pulley so operators do not have to go near a potential pinch point. In keeping with the overall goal of simpler plant maintenance, the Magna – Skin Technologies magnet mounted on the secondary crusher feed belt has no moving parts (other than a hydraulic lift), unlike side discharge designs that typically incorporate drive motors and belts. In operation, the magnet removes and holds tramp metal from the crusher feed for later removal during plant servicing. The same conveyor belt has a folding top section that allows clear access to the crusher for liner changes and thereby avoids trailer moves to create the necessary clearance. In addition, plant set up flexibility is increased by integral feed conveyor support on the crusher trailer frame, allowing to crusher be set up on either side of the screen plant as required. Finally, the CH660 crusher is controlled by the Sandvik ASRi crusher control system which Polowy is utilizing to obtain a balance of productivity and quality.
The second TBG Contracting plant seen was utilising pit run to produce 75 mm minus granular base. Here, a pan feeder fitted with a 600 mm opening grizzly regulated feed to an ElRus 3054 jaw crusher. From there, material was conveyed to a 1.2 m wide belt feeder with variable drive adjusted from the control tower. The feeder regulated material flow to an ElRus 6 by 20 double deck screen with oversize from the screen reduced by a Sandvik S4800 cone crusher. Finished product was stockpiled by a 46 m Thor radial stacker. One noteworthy aspect of this plant was the available capacity for electricity generation, with two Caterpillar 3412 and Caterpillar 3306 generator sets, all in a single trailer. The two large generators can together supply 1600 amps when required while the plant runs off the 3306 generator set in service mode.
Surmont Sand & Gravel Limited
At another pit location, the spread of Surmont Sand & Gravel Limited was utilising pit run to make 75 mm minus road base. Here, a Caterpillar 988H wheel loader discharged pit run into a hopper equipped with a variable speed belt feeder. This unit regulated feed to a jaw screener plant where the feed discharged onto a double deck Terex Cedarapids 6 by 16 screen fitted with 64 mm and 3 mm screen cloths on the upper and lower decks respectively. Material larger than 64 mm retained on the upper deck was reduced by the unit’s 3647 Metso Nordberg C96 jaw crusher. At the same time, minus 63 mm plus 3 mm material bypassed the jaw while pit run material already smaller than 3 mm was stockpiled. Crushed material from the C96 and bypass material were then conveyed to a Metso Nordberg 7 by 20 back fed triple deck screen. Here, 75 mm minus product went forward for stockpiling while oversize was directed to a Metso Nordberg HP 400 cone crusher in closed circuit with the screen. At this plant, production had just got underway and a large stockpile area had been levelled in anticipation of large inventories. As a result, product was being conveyed out to a KPI-JCI 900 mm by 46 m Superstacker by three Kolman 900 mm by 18.3 m long field conveyors, with the third Kolman carrying a Belt-Way Scales Inc scale.
As a footnote on the topic of inventories, keeping track of raw material extraction, truck shipments and product inventories is a significant task on its own given the level of activity at Susan Lake. In addition to comprehensive scalehouse records, monthly volumetric ground surveys are completed by the oil companies to measure extracted volumes and, as a further check, aerial surveys are completed each year to independently verify bank extraction and stockpile volumes.
|What is oil sand?
Oil sand is made up of grains of quartz sand, surrounded by a layer of water and clay and then covered in a slick of bitumen. Alberta’s oil sands are contained in three deposits (Athabasca, Cold Lake and Peace River) and cover an area the size of New Brunswick. The entire area comprises the largest single deposit of oil in the world, containing between 1.7 and 2.5 trillion barrels.
Oil sand is recovered by surface mining or in situ technology and, once mined, bitumen is separated from the sand using a patented hot water extraction process. The oil sand is first mixed with hot water to form a slurry which is then transferred to a separation vessel via a pipeline (hydrotransport). There, the slurry separates into three distinct layers; sand settles on the bottom while middlings (sand, clay and water) sit in the middle and a thin layer of bitumen froth floats to the surface. The bitumen froth is skimmed off and spun in centrifuges to remove the remaining sand and water before going to an upgrading plant. The leftover sand, clay and water are pumped to large tailings ponds and the water is recycled back to the extraction plant for reuse.
For more information go to www.oilsandsdiscovery.com