Waste polythene and polypropylene — consisting mainly of discarded bags and biomedical waste — are subjected to `catalytic cracking' or breaking down the carbon chain. The correct ratio of the catalyst and the plastic materials are taken in the reaction flask to get greater yield.
When heated at 400 degrees Celsius, the plastic yields a distillate crude. Fractional re-distillation yields a type of petrol at between 100 to 120 degrees C and kerosene at between 150 to 180 degree C. Finally, the process leaves diesel as residue.
In about two hours, the students were able to generate around 2 litres of crude from 2.5 kg of plastic waste and through distillation one litre of petrol and half a litre each of kerosene and diesel. The cost works out to roughly Rs. 22 for petrol and Rs. 26 each for diesel and kerosene.
Sridhar says by heating plastic in the absence of oxygen, toxic dioxin emissions are also avoided, making the fuel eco-friendly. Even the left over paraffin mass (approximately 500 gm) can be made into candles.
In the recent months, the Engineering colleges in and around Chennai have been coming up with interesting gadgets, processes or concepts. The Hindu has been covering most of them in its City Column. There have been several interesting inventions in micro-machines, microprocessors etc. These inventions may probably qualify only as toy-gun stuff, but what is gratifying is to see the engineering students jumping in to develop such interesting things and choosing them as projects. When I studied in IIT Madras we did nothing of this kind. We worked on boring and useless theoretical topics as our B.Tech projects.
News coverage in The Hindu shows that these developments are in fact coming from self financing engineering colleges with no Government support. The teachers in these colleges must be quite average, and are probably paid low salaries. This shows that the students should be quite smart and tenacious in wanting to do something unique and challenging. Good luck to them.