HomeIndustrial MineralsAMBATOVY'S ACID PLANT


The US$3.25 billion Ambatovy nickel and cobalt project, located in Madagascar 10 km to the south of Tamatave, is set to begin production in 2010 after construction began last year.

The project is owned by Sherrit International (40%), Sumitomo (27.5%), Korean Resources Corporation (27.5%) and SNC Lavalin (5%), (the project engineering procurement construction management (EPCM) contractor). Included in that project cost is the work being done to ensure it has a minimal impact on Madagascar’s environmentally sensitive tropical forest land where it is located. The actual nickel-laterite mine site is 200 km inland, with the processing plant located near the port of Tamatave.

Ambatovy has an ore reserve of 125 million tonnes containing
1.04% nickel and 0.10% cobalt, and a projected life of mine of over 25 years. The near surface deposit will be extracted by open pit mining. The project will produce 60,000 tonnes of London Metal Exchange (LME) nickel and 5,600 tonnes of cobalt a year.

Bateman Engineering, which won the engineering and procurement (EP) contract for the sulphuric acid plants, is undertaking this portion of the project, itself worth about US$100 million. This project was tendered for out of Bateman’s European offices and the engineering procurement contract excludes shipping. The company was asked to bid on the shipping, with the plant to be delivered at the port of Tamatave some 10 km north of the site.

Bateman senior project manager Michael Hughes says the target is to have the EP contract completed by mid-March 2009 and operational by end-September that year. Bateman is working with technology supplier Noram Engineering and Constructor’s of Canada, which is supplying the acid producing technology. “We have an exclusive agreement with Noram for use of its proprietary technology in sub-Saharan Africa and Noram will undertake about 60% of the engineering on the project,” Hughes says. Ambatovy is Noram’s first greenfield project outside north America, where it has strong credentials.

The rest of the design is being undertaken by Bateman, and the fabrication is outsourced mostly to China by Bateman.

The sulphuric acid plants will melt elemental sulphur brought to the site in bulk format. This will then be filtered to remove contaminants before being burned in a sulphur furnace and oxidised by dry air to form sulphur dioxide (SO2). The SO2 will be fed into converters where it will be oxidised in the presence of a vanadium-pentoxide catalyst to produce sulphur trioxide (SO3). This SO3 will react with water in absorption towers to form sulphuric acid of at least 98.5% concentration. At full production the facility, which will consist of two stand alone acid plants, will produce 5,500 tonnes of acid a day. Bateman is doing the project off-site with the plant to be delivered in as complete a form as is possible to ensure ease of construction, ensure quality, reduce the construction time taken, and also eliminate safety problems on site. The largest pieces of equipment to be delivered in one piece are the converters at a diameter of 14.5 metres, a height of 24 metres and a weight of 330 tonnes each. “The converter, manufactured in Durban by Metso ND to Noram design drawings, will be shipped vertically,” Hughes says. “Metso was awarded that contract based on overall quality, cost and capacity to produce compared with very low cost centres in Asia. It shows South African suppliers can have a slice of the pie and are cost competitive on higher technology items such as the converter which includes an internal heat exchanger.”

The fabrication of less specialised portions of the plant is being done in China. “They have the capacity to do the job with shorter lead times than the oversubscribed South African fabricators.”

Acid plant projects are not new to Bateman. Hughes says that Bateman has done five acid plants in the past, but none of them in the last 15 years. “We were indirectly involved in the acid plant at Skorpion Zinc in 2002, which was engineered under Monsanto licence and built by Grinaker-LTA.” More direct involvement came in the Rossing Uranium acid plant in 1976 and a plant at Buffelsfontein in 1979.

Sulphuric acid technology has not fundamentally changed in the past 60 years and over the last 18 years Bateman’s technology partner, Noram, has improved on certain designs and made the incremental improvements in performance that means a slightly smaller and more efficient plant is designed than a few decades back. The Noram improvements have resulted in less downtime and significantly improved operational expenditure. An example is the acid distribution system, where cleaning takes about two hours, as opposed to two shifts as was the case in the past. People do not have to enter the towers but can clean them from outside, which is a lot safer. Noram also brings its patented anodic protected acid coolers and cold and hot heat exchange Radial Flow and Split Flow technology. CECEEB HP Saddles of ceramic also greatly assist in pressure drop control on these plants.


Schematic of a 5,500 tpd
acid plant.

Apart from the big plus provided due to its relationship with Noram, Bateman won the contract because of its proximity to Madagascar. “The client, Sherrit International, based in Canada, was looking for an EP company that understands the region and conditions, and also has the resources and people available to do the job,” Hughes says.

At overall construction peak, the Ambatovy project will have some 7,700 people working on it. The steady state mine will employ 400 people with another 1,200 working at the plant. For the acid plant engineering, there are about 30 people working on it from Bateman, with another eight people working on it out of the Noram offices.

Bateman has used 3D design and the project has gone smoothly, Hughes says. One of the reasons it has gone so smoothly is because of the effort taken to find good suppliers. Representatives from Bateman’s Chinese office, as well as Hughes himself, went to inspect the suppliers’ quality of work and ensured it was dealing with the best of the best fabricators in China.