Characteristics of syngas from pyrolysis and CO2-assisted gasification of waste tires

The growing problem of waste tire generation worldwide can be converted from a major environmental issue to a valuable energy source using the thermochemical conversion processes. CO2 gasification can offer a prominent position in the tire waste to energy panorama since it offers high quality syngas production and direct mitigation pathway for greenhouse gas emissions. An evaluative study of syngas yield and quality between pyrolysis and CO2 assisted gasification has been carried out in a laboratory scale fixed bed reactor in this work. Pyrolysis was performed in the temperature range of 673-1173 K and gasification at temperatures of 973-1273 K in steps of 100 K. Flow rates of syngas and its major gaseous components (CO, H-2, CH4 ) for both the processes and on CO2 consumption during gasification were reported. The results provided direct comparison between pyrolysis and gasification and also on cold gas efficiency. Results showed that gasification temperature strongly affects the syngas yield, quality, and energy content. Gasification reactions below 973 K were negligible. Char reactivity even at higher temperature was found to be low. Gasification resulted in 3.3 times increase in CO yield at 1073 K and 2.8 times increase at 1173 K as compared to pyrolysis. The increase in gasification temperature from 1173 to 1273 K enhanced CO yield by 1.5 times. While pyrolysis provided higher efficiency from a merely energetic point of view, gasification still presented high cold gas efficiency of 62.6% at 1273 K and an overall efficiency greater than 30%. In addition, CO2 assisted gasification of waste tire provided a direct pathway to utilize green-house gas that showed carbon dioxide consumption of 0.75 g/gram of scrap tire gasified at 1273 K, and produced significant amounts of valuable CO, which offers good value for both energy production and fuel, and to value-added products with further synthesis.