About 70% of the cast metal objects around us, from bathroom taps to automobile gearboxes, are manufactured in foundries using a method called sand casting. Molten metal is poured into moulds made from green sand—a mixture of sand (about 80%) and clay (about 10%). At high temperatures of about 1500℃ required for casting, clay forms a coating on the sand particles, and the sand becomes unusable for further casting. The disposal of such sand has severe environmental and cost implications, particularly for small foundries. In a new study, researchers from the Indian Institute of Technology Bombay (IIT Bombay) have demonstrated a practical and economical way to reuse this green sand.
Although existing methods for reclaiming green sand are capable of processing many tons of sand per hour, they are expensive. Since about 80% of the 4600 foundries in India are of small and medium scale, these methods are unaffordable for them as these foundries can reclaim only about 1000 kg of sand per day. The only viable solution then is to dispose of the green sand by dumping them in water bodies and land. Since used green sand contains heavy metals like lead and tin, which leach into the ground causing water pollution, environmental laws restrict such dumping. On the other hand, buying fresh sand is now expensive since sand mining is banned in most states, further increasing the cost for small and medium scale foundries. Thus, reclaiming used green sand in a cost-effective and scalable approach turns out to be an attractive proposal.
Read more: IN – GOING GREEN BY RECLAIMING GREEN SAND
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