Towards circular flows of tungsten - Characterizing dissipation

• Tungsten has many unique properties. It has the highest melting point of all metals, a density comparable to that of gold and a high thermal conductivity. More than 50% of tungsten is used in hard material applications such as tungsten cemented carbide (WC-Co) tools for metal cutting and wear applications. However, tungsten can also be found in filaments in light bulbs, catalysts, paint, and a number of other applications. Tungsten has a high economic value and global resources and reserves are mainly located in China, which is why tungsten qualifies to the European Commissions´ list of so-called critical materials. Furthermore, the dissipation of tungsten in its use phase is considerable: About 60% of the tungsten that is used in different applications worldwide dissipates (i.e., is not recycled or reused). This constitutes a hindrance for circular material flows of tungsten. It is recognized that tungsten dissipates through emissions to the environment, flows to landfill and dilution in other material flows, but their relative share remains unknown.The aim of this study is to characterize the dissipation from tungsten hard material applications in the use phase in order to identify possibilities for recycling and other strategies towards circular flows of tungsten. The method of substance flow analysis (SFA) is used to quantify global flow of tungsten hard materials with a focus on the use phase of tungsten hard material applications and associated dissipation. Preliminary results indicate that dilution in other material flows constitutes the largest part of the dissipation. The dilution happens partly through recycling processes that target other metals than tungsten. This is in line with recent suggestions made by Leal-Ayala et al., (Resour Conserv Recy, 103: 19-28, 2015). Our results also indicate that emissions, although they comprise a minor share of the total dissipation in the use phase, might be important from an environmental perspective. Recommendations on steps towards making tungsten a future circular material are provided and include having a higher resolution in recycling processes.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering (hsv//eng)

Nyckelord

cemented carbide

tungsten

substance flow analysis

dissipation

circular economy

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