Background

Nissan Casting Australia creates complex automotive components from molten aluminium, including engine cylinder heads, oil sumps and gearbox casings. Each year the site in Dandenong processes around 8000 tonnes of aluminium into approximately 2.5 million individual automotive components. These are sold to local and overseas auto manufacturers, with annual sales in excess of $50 million.

The Dandenong site receives daily molten aluminium deliveries from Simsmetal (located in Brooklyn) that are kept in their molten state in holding furnaces on-site. Additional molten aluminium is produced by adding aluminium ingots and scrap to melt furnaces as required. Nissan have been exploring a range of possible improvements to melt furnace operation in order to deliver a range of benefits including increased plant energy efficiency, productivity, responsiveness and safety.

The Project

Sustainability Victoria is partnering with Nissan Casting to investigate the feasibility of a number of initiatives to improve the energy efficiency of the aluminium melting process at its Dandenong operation, in particular the melt furnaces.

The options being considered include the retrofit of regenerative burner technology to the existing melt furnaces, the installation of a new tower melt system with heat recovery facilities, and the retrofitting of an existing furnace with regenerative burners and having it discharge directly into the holding furnace. These new technologies recover the heat in the waste gases from the melting to allow more efficient operation.

The installation of a regenerative (recuperative) burner unit will recover heat from the combustion gases to preheat the incoming combustion air. Energy efficiency improvements of up to 40% can be achieved, but the project payback is not viable due to the initial high capital cost.

Alternatively, a tower melt furnace may be installed which utilises particular technology to melt metals to a liquid state. This technology is considered to be substantially more efficient at melting metal compared with wet bath furnaces and intrinsically safer for operators and has a better payback due to the labour saving and dross loss savings of the new technology.

A third option for Nissan involves the retrofit an existing melt furnace with regenerative burners to convert it to a batch melt operation, with melt transfer into an adjacent holding furnace.

Sustainability Victoria support will focus on evaluating the heat recovery aspect of the tower melt system and facilitating exploration of the full range of options. It will include a detailed design and implementation plan of preferred melt furnace modifications, including the preparation of a drawing package for construction, establishing firm costs, and the provision of miscellaneous implementation assistance, including integration works and approvals.

The project began in May 2005, with the feasibility study conducted from December 2005 to August 2006, and final capital approval to be granted by April 2007. The chosen option is expected to be implemented by December 2007, with the estimated capital investment costs to implement the project being between approximately $1.4 million.

Project Benefits

Energy reductions of up to 40% in furnace energy use have been achieved at other sites by retrofitting of furnaces with regenerative burner technology. Additional benefits from retrofitting include plant productivity gains and reduced oxidised metal losses.

The installation of a tower melt furnace offers a significant range of benefits over the current practice of manually loading metal directly into molten aluminium in melt furnaces, particularly in regard to improved operator safety, maintenance and increased plant output, and responsiveness to short-notice orders.

Nissan Casting is aware of only three other sites in Australia that use tower melt systems and of no other die casting company in Australia utilising regenerative burner technology. Both technologies have been applied overseas, however, and greater application in the Victorian die casting industry would stoke local innovation.

The projected energy saving is estimated at 33,000 GJ per annum with a total greenhouse abatement of 1,900 tonnes per annum – equivalent to removing 435 cars from the road. The net savings from energy efficiency, productivity, labour reduction, maintenance and other savings is estimated at $370,000 per annum, with an overall project payback estimated between three and four years.