A novel chemical pre-pyrolysis treatment of waste tyre crumbs: a viable way for low temperature waste tyre pyrolysis

Abstract

Pyrolysis of tyres is a process that consumes non-renewable energy resources, and is characterised by the requirement of a significant amount of energy. For example, natural rubber and styrene-butadiene rubber require 300-350 °C and 400-450 °C, respectively, to decompose under inert nitrogen conditions. The current study aims, firstly, to reduce the temperature typically used for waste tyre crumbs pyrolysis to minimise the energy requirement of the process as well as to improve the quality of the liquid fraction of the pyrolysis product, tyre derived oil (TDO). Before pyrolysis, waste tyre crumbs were first treated with a mixture of chemicals, dried and then pyrolysed using a 40g vertical fixed bed reactor. The results acquired from the ultimate analyser for the CHNS illustrated a decrease in carbon from 80.6% to 57.2% and an increment in nitrogen (from 0.4% to 6.5%) and oxygen (from 9.7% to 30.2%) in the treated tyre crumbs. FTIR results indicated that oxidation took place in the treated sample by displaying the presence of oxygenated functional groups in the spectrum, which agreed with CHNS results. The temperature was reduced drastically from a minimum of 400 °C to a minimum of 100 °C for pyrolysis, and therefore, resulting in a lower initial/starting pyrolysis temperature range of 100 -115 °C. In addition, approximately 87wt.% pyrolysis yield was obtained out of 60% pyrolysable substances in a tyre at the final temperature of 280oC. The differential thermogravimetric analyser (DTA) was used to confirm the extent to which pyrolysis experiments took place in the feedstock by analysing the char after pyrolysis. The current study is set to improve the pyrolysis of waste tyre crumbs by significantly reducing the temperature and time of the process, which lowers the operation cost required for the tyre crumbs’ pyrolysis process.