Overview

Before steel can be coated with zinc in the conventional hot-dip galvanising process, it is first dipped in acid to dissolve any old zinc or iron (as rust) that would impede the zinc bonding process. Over time, the 'pickle liquor' acid decreases in acid strength while building up zinc and iron contamination, and thus the 'spent pickle liquor' is periodically removed for treatment and disposal.

The usual method of disposing of spent pickle liquor produces 2.3 tonnes of waste for every tonne of spent pickle liquor treated, including 600 kg of metal-bearing waste that is sent directly to landfill. Intec's proposed solution instead extracts and recovers the useful iron and zinc into useful products, and recycles the clean acid back for reuse, offering an economic, environmentally-superior zero-waste outcome.


The Intec Process: A Cheaper Alternative with Better Environmental Outcomes

Using the Intec Process and associated know-how, Intec has developed a process flowsheet for the proposed zero-waste recycling of zinc-bearing spent pickle liquor from the galvanising industry.

EPA Victoria has approved $780,000 of funding through the HazWaste programme to support the demonstration of this proposed flowsheet at Intec's Sydney and Burnie facilities, and for the construction of a facility in Victoria to treat at least 1,000,000 litres per annum of spent pickle liquor.

The first phase of testing commenced in November 2009, and Intec will continue to update the market as information becomes available.

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International Prospects for Wider Application of the Technology

It is worth noting that approximately half of the world's annual consumption of zinc (over 5 million tonnes of over 10 million total tonnes of zinc consumption per annum) is used in steel galvansing. While the economic, regulatory and technical drivers will vary from country to country, Intec expects that the Intec Process application for spent pickle liquor recycling will, once proven in the current project, be readily applied in multiple projects worldwide.