Pyrolysis of waste tyres in an atmospheric static-bed batch reactor: Analysis of the gases obtained

摘要

Scrap tyre pyrolysis was studied under nitrogen atmospheric pressure in order to analyse temperature influence on the global yields and the gas composition. A static-bed batch reactor was used to pyrolyse 300 g of shredded scrap tyres at temperatures from 400 to 700℃. The reactor was externally heated by means of electrical resistances, the heating rate being approximately 12 K min~(-1). Once the required system temperature was reached and stabilised, it was maintained for 4 h. The residence time of the gas in the reactor was calculated, with values falling between 1 and 1.5 min. Three phases were obtained after pyrolysis: solid (char), liquid (water and oils) and gas (light hydrocarbons, H_2, CO and CO_2). The product distribution and composition were studied as a function of the thermal treatment. Global yields were determined as follows: char, 47-63 wt.%, oils, 30-43 wt.%, and gas, 2.4-4.4 wt.%. It was observed that the liquid yield increases with temperature from 400 to 500℃. However, from 500℃ on, this parameter remained almost constant. The solid yield followed an inverse trend to that observed for the liquid yield. On the other hand, the gas yield showed a slight continuous growth with temperatures ranging from 400℃ (2.4 wt.%) to 700℃ (4.4 wt.%). The gas phase was analysed off-line by gas chromatography. The main gases produced from the pyrolysis process were H_2, CO, CO_2 and hydrocarbons: CH_4, C_2H_4, C_3H_6 and C_4H_8. It was observed that the fraction of light gases (H_2, CO, CO_2 and CH_4) was greater at higher temperatures.