Engineering & Mining Journal

APR 2017

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 29 of 83

CONCENTRATES 28 E&MJ • APRIL 2017 While most of the mineral cargoes lost at sea sink to depths well beyond practical or economic salvage, an exception — wit- nessed by this author — occurred in June 2003 when a vessel carrying some 3,300 metric tons (mt) of zinc sulphide con- centrates from the Tara mine in Ireland was wrecked on an island off the remote northwest coast of Scotland. The ship, the Jambo, had loaded in Dublin and was heading towards the Odda zinc refi nery in Norway when it veered off course and hit Eilean Fada Mòr in the early morning of June 29 th . Having grounded, it took on water and subsequently sank, com- ing to rest with its bow exposed and its stern at a depth of around 30 m (100 ft.). The subsequent enquiry determined that crew fatigue was the principal cause of the accident. The near-pristine waters off north- western Scotland host an important lo- cal fi shing industry, with initial concerns over the impact that concentrate leach- ing might have on local fi sh and shellfi sh stocks. With the ship's fuel load recov- ered, the U.K. government entered into an agreement with the Protection and Indemnity (P&I) Club that had underwrit- ten the Jambo's insurance, agreeing to underwrite 50% of the cost of recovering the cargo. A contract was awarded to the Dutch company, Smit Salvage, which mobilized a six-ship fl eet including three self-pro- pelled hopper-split barges, a towed barge equipped with a heavy-lift crane, diver accommodation and generators, and two tugs. Using water-jets, divers broke up the bulk concentrate remaining in the Jambo's hold, with the resulting slurry being pumped into the barges. Beginning in July 2003, the opera- tion continued until mid-October, when the government's agreement with the P&I Club expired. By that time, Smit had re- covered around 1,900 mt of concentrate, with the remainder effectively lost on the seabed. Major obstacles to the operation had included zero visibility for the div- ers working in the hold, the density of the fi nely ground concentrate — which caused it to resettle quickly before the pumps could suck it to surface — and the long settling time needed in the barges before surplus water could be decanted overboard and more slurry loaded. Weather systems rolling in from the Atlantic also caused delays, so what was originally intended to be a two-week op- eration extended to nearer 10. And while the operation marked a major change in political will towards minimizing the po- tential impact of mining and its products on the environment, this was a rare in- stance where circumstances allowed re- covery to take place. As it happens, long-term monitor- ing has indicated that the residual cargo has had no signifi cant effect on marine life in the area, and the wreck — now com- pletely submerged and overturned — is a popular amateur dive venue for those har- dy enough to brave the frigid Scottish sea. Case Study: Recovering Sunken Zinc Concentrates Two of the hopper-split barges, which have a hull that is specially designed to handle highly fl uid cargoes. When fi lled with slurry, each barge was taken off-site to allow the concentrate to settle before the surplus water was decanted. of its range is its 20 ft. copper concen- trate container, which has a capacity of 20.5 m 3 and a payload of just over 30 mt. Made of steel with a tare weight of just 3.45 mt, the container is designed to be compatible with all tipplers in the Australian market, and includes a lid that is automatically locked and unlocked by the tipplers. The company has produced 1,400 of these units for OZ Minerals, which are used for transporting copper concentrate from the Prominent Hill mine in South Australia to the port of Adelaide. Other containers in ISG's 'Pit-to-Ship' range include a 20 ft. unit designed for handling nickel concentrates, and a 20- ft. half-height unit for iron ore, as well as those designed for handling bulk coal, fi t- ted with tarpaulin covers. And the company does not only supply the domestic Australian market. Over- seas, ISG has won orders from Codelco for copper concentrate containers, from Exxaro for 1,350 iron-ore containers for an operation in the Congo Republic, and from MMG for 1,200 copper concentrate units for its Las Bambas mine in Peru. The Las Bambas concentrate-handling project, which won the innovative technol- ogy award from International Bulk Journal last year, involves transporting 1.4 million mt/y of concentrates 443 km by road to the nearest railhead, then a further 286 km to the port of Matarani for export. The 17.5 mt-capacity ISG containers are de- signed to fi t two per truck and three per rail wagon in order to meet local weight restrictions. Empty containers arriving at the mine have their lids removed before being fi lled by wheel loaders, after which the truck wheels are washed, the contain- er rims vacuumed and the lids refi tted. Trucks are then sent in convoys to the rail transfer station, where the containers are FIBCs (big bags) being loaded on to a road trailer.

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