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A NEW system that enables the recovery and recycling of argon from silicon and sapphire production has just been launched.

The ArgonØ system can recover 95% of the waste argon from silicon vacuum furnaces, at a purity of 99.9998%. Argon is used during the process of growing single crystals and smelting polycrystalline materials for ingot production in the production of silicon ingots. However it becomes contaminated with carbon monoxide, methane, hydrogen and vacuum pump oil during use which means that the gas cannot normally be recycled and is vented to atmosphere.

Chemist Rob Grant – a former head of technology with BOC Edwards – worked with the chemical engineering department at Cambridge University to develop a chemical looping combustion reactor (CLC) with a solid state oxygen carrier that combust the impurities to CO₂ and moisture, which are removed via molecular sieve traps. The eight-hour process can also be adapted to recover helium.

The silicon industry uses considerable quantities of argon – Grant says that a large silicon plant typically has over 100 furnaces running 160 silicon production cycles a year, each of which requires up to 150 m³ of argon. Recycling the gas would make the process more sustainable as well as cheaper – the annual argon bill for a large silicon producer easily comes to US$1m/y, Grant says.