The tar sands-produced tailings ponds – contaminated with toxic chemicals such as naphthenic acid and polycyclic aromatic hydrocarbons – occupy some 170 square kilometres of northern Alberta. It is an industry imperative – to stem growing environmental criticisms – to mitigate this situation somehow. Their approach is to use technology.
The Financial Post reports today that, “Royal Dutch Shell PLC believes it has invented a system that will dramatically speed up the process of cleaning up tailings ponds – the toxic waste pools necessary to mine Alberta’s oil sands — and is willing to give the blueprints away to anyone, competitors included, for free.”
“Shell calls its new system ‘atmospheric fines drying’, and Thursday said it received regulatory approval (presumably from the Alberta Energy Resources Conservation Board and Alberta Environment) to proceed with a commercial-scale demonstration project. …Mature fine tailings – the fine clay particles suspended in water – are at the heart of the tailings pond dilemma. These tailings take decades to settle in the ponds, which has to happen before the massive lakes can be reclaimed. …Shell plans to barge mature fine tailings from its tailings ponds into a drying structure. It will mix the tailings with thickeners, and spread the concoction on a sloped surface, allowing the sun and gravity to extract the water from the grayish goop. The water will be reused in the mining process, and the clay layers will pile higher as more mature fine tailings are spread to dry.”
The Globe and Mail further explains that, “The (Shell) plant adds a chemical to the tailings, called a flocculant, that helps to thicken them into a sludge. It then sprays the sludge onto the sides of a 30-hectare sloping pit, where water drips from the tailings and leaves behind a solid substance that looks a bit like wet sand. Shell said the technological breakthroughs lie both in the flocculant it is using, and the process of placing down the sludge in such a way that water efficiently drains away.”
“The plant is expected to dry out 250,000 tonnes of tailings by year’s end. … (Shell says) that the new plant will process somewhere between 1 and 20 per cent of the company’s mature fine tailings. It did not describe the costs of operating the technology, nor did it say how much it could reduce its tailings pond needs.”
The Globe and Mail adds that, “Suncor Energy Inc., by contrast, has said its own new drying technology will both reduce its tailings pond requirements and save it money. …Suncor is the only company pledging to meet the requirements of Alberta’s Directive 74, which requires oil sands companies to dry out 50 per cent of their fine tailings by 2013.” The National Post reported in October 2009 that, “Suncor’s new technology will mix mature fine tailings with polymer flocculant – a thickner – and then deposit that in thin layers over sand beaches with shallow slopes, the company explained.”
WHAT THE FLOCCULANT?
What is the polymer flocculant that Shell and Suncor use for the tar sands tailings ponds? According to web-based sources, it refers to chemicals that promote flocculation by causing suspended particles in liquids to aggregate, forming a floc. The following chemicals are used as flocculants: alum, aluminium chlorohydrate, aluminium sulfate, calcium oxide, calcium hydroxide, iron(III), chloride iron(II), sulfate polyacrylamide, polyDADMAC, sodium aluminate, and sodium silicate.
To read more, go to http://www.financialpost.com/news/Shell+touts+tailings+pond+solution/3447159/story.html#ixzz0xnpUE25u and http://www.theglobeandmail.com/report-on-business/industry-news/energy-and-resources/shell-opens-plant-to-clean-up-oil-sands/article1686706/.
