Fixed Bed Pyrolysis Reactor

Fixed bed pyrolysis reactors, as shown in Figure 4, are relatively simple to construct and efficient at producing clean fuel. These reactors are typically operated in batch mode. The waste tyre is fed into a fixed bed inside a cylindrical steel pyrolyser. Heat is supplied to the waste tyre via the pyrolyser wall by an electrical heater or furnace mounted around the reactor. By purging pressurised nitrogen (N2) from the external cylinder, all the oxygen inside the pyrolyser is eliminated. When waste tyres decompose, solid char accumulates at the bottom of the pyrolyser, while vapour (both condensable and non-condensable) escapes to the top. The vapour is then cooled by a condenser, which condenses the condensable vapour into oil, which is then stored and collected in a liquid storage container. The non-condensable vapour remains gaseous and is collected as syngas [74]. The basic characteristics of fixed bed reactors are higher carbon conservation rate, lower velocity of gas, lower gas carryover rate, and a long residence period of solid. Generally, small-scale heat and power applications are considered for these reactors [75,76]. The removal of tar from fixed bed reactors is a major issue; however, recent advances in thermal and catalytic tar conversion have provided a possible solution to eliminate the problem [77–79]. In a 1.15-L, nitrogen fixed bed reactor in a temperature range of 400–700 ◦C, Aydin and Ilkilic [17] investigate the pyrolysis of waste tyres in stationary reactors, with removed fabric and steel. The oil output increase from 31% at 400 ◦C to 40% at 500 ◦C, and the return at higher temperatures increased slightly. Kar [67] investigated the effect of pyrolysis temperature ranging from 375 to 500 ◦C in a laboratory model fixed bed pyrolysis reactor. The highest oil output of 60.0 wt% oils was reported to be attained at 425 ◦C in this study. However, the oil output reduced to 54.12 wt% at higher pyrolysis temperatures, at 500 ◦C. The output of gas increased from 2.99% to 20.22%W while the output of char fell from 50.67% to 26.40%, with pyrolysis temperature increasing from 375 ◦C to 500 ◦C. In a similar pyrolysis reactor, Banar et al. [34] obtained 38.8 wt% of oil, 27.2 wt% of gas and 34 wt% of char at 400 ◦C pyrolysis temperature. The study further investigated the effect on waste tyre pyrolysis on the heating rate and found that the heating rate was influenced by a decrease in oil production to 35.1 wt% and gas yield to 33.8 wt% as the heating rate increased at a pyrolysis temperature of 400 ◦C from 5 ◦C min−<sup>1</sup> to 35 ◦C min<sup>−</sup>1.

**Figure 4.** Diagram of a fixed bed pyrolysis reactor.
