Jericho Processing Plant

Tahera capitalized on experience from the Ekati and Diavik plants, designing the Jericho plant to be much smaller and more compact, with limited equipment redundancy. The design capacity of the Jericho plant is 2,000 tonnes/day. A minimal plant footprint was used to reduce the capital costs for concrete foundations, building steel, cladding and installation, and also the heating costs for the processing plant. To achieve the small building footprint, materials conveying had to be based on vertical lift, pocket-type conveying belts rather than conventional troughed conveyor belts, allowing the facility to be built on a 42-m x 42-m, 1,750-m2 footprint.

From May to July 2004, Hatch Ltd. undertook the basic engineering and flowsheet development for a new feasibility study, doubling the initial plant to a 100-tph processing facility. The detailed engineering and procurement phase took place from August 2004 to March 2005. Hatch provided construction assistance from June 2005 to mid-January 2006, and commissioned the plant two weeks later. On February 1, 2006, the plant was handed over to Tahera’s operations team for production ramp up, operations training and plant familiarization.

Run of mine ore measuring -400 mm is fed through a static grizzly onto a 1.2-m-wide Metso apron feeder that delivers the material to a 500-mm MMD double-shaft-toothed rolls crusher producing nominally -70 mm material. The crusher product is collected by a pocket-type conveyor belt and elevated to a 2.4-m-diam x 6-m Metso scrubber. The scrubber discharge is sized on a 2.4-m x 4.8-m Vibramech double-deck screen at 25 mm and 1 mm. (All conveyors are by Strongco, and slurry pumps are by Warman.)

The +25-mm coarse oversize from the scrubber screen discharges onto a pocket belt conveyor and is elevated with the -25+8-mm heavy media separation (HMS) recrush material into a 50-t surge bin. A variable speed conveyor withdraws material from the bin to a 0.6-m-wide x 1.2-m-diameter Koppern high pressure grinding roll (HPGR). The HPGR product is conveyed to the scrubber conveyor.

The -25+1-mm HMS feed fraction is elevated by a pocket belt conveyor to a 50-t surge bin. A variable speed feeder withdraws material from the bin to a 100-t/h DRA HMS plant. The -25+8-mm low density material is conveyed to the HPGR feed bin, and -8-mm material is conveyed to the rejects stockpile outside the plant. The HMS concentrate discharges into a 5-t bin and is pumped 20 m to the top of the recovery section.

The recovery section consists of a ‘simplified flowsheet’. The HMS concentrate is sized on a 0.6-m x 3.6-m horizontal screen, and stored in 1-t bins. The -4+2-mm fraction is treated over an Eriez rare earth wet high intensity magnetic separator (WHIMS). The +2-mm concentrate fraction is processed in batches by two in-series Ultrasort wet x-ray machines. The x-ray concentrates are dried in an infrared drier and discharge into the sorthouse feed bin. The smaller (-2-mm) concentrate fraction is treated on a 1.2-m-wide Vibramech grease table; the second pass x-ray machine rejects are treated over a second grease table. The grease table rejects are conveyed to an outside stockpile.

The diamonds are cleaned on site using a caustic fusion process prior to valuation by a government agent.

Adjacent to the plant is the Long Lake impoundment area for the fine processed kimberlite. The -1-mm fines slurry (10-15% of the processed kimberlite by weight) is pumped to a degrit cyclone, the overflow of which is laundered to a 6-m-diam deep-bed Ultrasep thickener. The thickened fines (2-4% of the plant feed) are pumped to the impoundment area where they consolidate over time. The cyclone underflow is dewatered on a vibrating screen and conveyed to an outside stockpile for disposal with the -8-mm HMS rejects.

Mike Rylatt is a consultant with Hatch Ltd. based in Montreal, and can be contacted at MRylatt@hatch.ca.