No abstract

Polycyclic aromatic hydrocarbons (PAH) emitted from fluidized bed combustion have been reviewed. Firstly, the PAH origin is undertaken. Secondly, the state of the art on their sampling and analytical procedures are commented. Finally, the influence of the fuel, fossil and nonfossil fuels, the combustor type and the combustion variables are analyzed concerning PAH formation and emission in solid/ gaseous phase.

Co-pyrolysis of forestry wastes and waste tyres is carried out using different facilities: a fixed bed reactor and a continuous auger reactor. Remarkably, only one phase is found in the liquid fraction, which is not achieved by mixture of the pure liquids. In addition, positive effects between waste tyre and biomass are evidenced, being more notable even synergetic in the auger reactor. It is found that whilst acidity, density and oxygen content decrease, pH and calorific value increase with respect to the merely biomass pyrolysis liquid, leading to upgraded bio-oil. Upgrading process is linked to the presence of radical interactions between waste tyres and biomass pyrolysis products. In addition, it is observed that the addition of waste tyres to the feedstock blend is significantly decreasing the amount of aldehydes and phenolic compounds, which is beneficial for improving the stability of the new bio-oils.

No abstract

No abstract

Scrap tires are a growing environmental problem because they are not biodegradable and the components used to manufacture tires cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tires by pyrolysis and hydropyrolysis has been studied using a swept fixed bed reactor. This is the first time that such a reactor has been used to carry out tire hydrogenation. The effect of the main process variables (temperature, heating rate, gas flow, reaction time, hydrogen pressure) on yields of oils, gases and solid residue has been determined. The oils, have been characterized using a combination of spectroscopic and chromatographic analytical techniques (TLC-FID, GC-MS, simulated distillation, and FTIR). While the main variable affecting tire conversion is temperature, oil composition is influenced mainly by hydrogen pressure, with the oils becoming lighter as the pressure is raised. No relationship between functional group composition of the oils determined by TLC-FID and FTIR and process variables was found. GC-MS showed that the oils are mainly comprised of single ring alkyl-aromatic species together with a large amount of limonene. Based on this finding, a possible reaction pathway for rubber conversion through polyisoprene depolymerization and further cyclization is discussed.

No abstract

No abstract