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Solar aluminium melting method cuts carbon dioxide emissions

19 June 2015

Using solar energy to melt aluminium, German and South African researchers are working on a project to reduce both electricity consumption and CO2 emissions.

Using mirrors to concentrate sunlight (photo: DLR)

South Africa has plentiful solar energy and, at the same time, possesses a large aluminium processing industry. Researchers and industry are cooperating within the SOLAM (solar melting of aluminium in a directly radiated rotary kiln) project to develop a method by which aluminium foundries could use solar energy to melt this metal.

The method would allow the companies to reduce their electricity consumption to a great extent and substantially lower their carbon dioxide emissions. Scientific institutions and companies from South Africa and Germany are collaborating in this project, which is coordinated by the German Aerospace Centre (DLR).

South Africa has vast reserves of natural resources, and local coal is still used for over 90 percent of the country's power generation. South Africa is among the world's 15 largest emitters of greenhouse gases, and the country itself is increasingly feeling the effects of climate change. Using a solar method to melt metals could substantially reduce carbon dioxide emissions and energy costs.

Solar rotary kiln designed for melting aluminum (photo: DLR)

Initially, the project partners will develop a 'rotary solar kiln', used to melt and recycle aluminium. A rotary kiln is not dissimilar to an elongated drum of a washing machine, rotating at low speed. This rotational movement constantly mixes the aluminium deposited in the drum, and ensures an even distribution of the solar derived heat.

Mirrors will be deployed to focus the Sun's radiation and achieve the required temperature of approximately 700°C. The system is to undergo testing on the solar tower at DLR's Institute of Solar Research in Jülich from 2017 onwards. This facility has over 2,000 mirrors designed to concentrate solar radiation on a point some 60m high, atop a tower.

A small rotary kiln is to be tested at laboratory scale using DLR's solar furnace in Cologne. These tests will involve melting small batches of aluminium scrap, and then analysing the quality of the molten aluminium. Industrial partner, AixProcess will use its process and flow simulation software to model the reactor and process. The researchers will take the calculations from the simulation to optimise the reactor, prior to scaling it for industrial application.

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