Waste tyre pyrolysis : sustainable recovery and reuse of a valuable resource

摘要

End-of-life car passenger tyres represent a major waste management problem, with more thanud450,000 tonnes of used tyres being generated each year in the UK alone (approximatelyud55,000,000 tyres). Recent legislation has made 100% material or value recovery from wasteudtyres an imperative.udThere are many different waste tyre management options available. The most commonly usedudprocesses include: retreading, use as fuel in incinerators and cement kilns and reprocessing toudproduce rubber crumb which has further applications in asphalt mixtures, carpet underlay andudplaygrounds.udThe theme of the research presented is a fundamental study and development of tyreudpyrolysis. Pyrolysis is an attractive method to sustainably recover valuable components of theudtyre rubber through the generated carbonaceous solid, oil and gas. Both conventional andudmicrowave-induced pyrolysis have been investigated. Microwave pyrolysis offers an excitingudalternative to traditional pyrolysis because of the potentially significant energy efficiencyudadvantage offered.udIn the first instance an investigation of the optimisation of the pyrolysis conditions byudstatistical design using conventional means to produce a carbonaceous solid char has beenudundertaken. This was followed by the investigation of microwave-induced pyrolysis usingudmodified commercially available microwave equipment as well as a bespoke and novel 2450udMHz, 2 kW rotary microwave furnace developed for the purposes of this project by CobhamudMicrowave Ltd. Carbonaceous solids produced by varying different experimental parameters,udsuch as power levels and pyrolysis duration are reported and analysed. In addition, the mainudconstituents of the oils generated have been identified and comparisons made with traditionaludthermal pyrolysis oil.udReuse of the solid residue is an important activity which has been researched. This char isudoften described as carbon black, but given that it contains all the solid, inorganic componentsudpresent in the tyre, as well as carbon black, it is better described as “char filler”. Theudsuitability of this waste tyre-derived char for reuse in the rubber industry as a filler substituteudhas been evaluated and is presented. The results show that the char has similar properties to audsemi-reinforcing filler with potential for improvement.