Co-pyrolysis of torrefied biomass and coal: Effect of pressure on synergistic reactions

Lumped chemical kinetic modelling of raw and torrefied biomass under pressurized pyrolysis

“…This included raw and torrefied wood (mixture of soft and hardwood species from South Africa) chips as well as raw pine (Pinus radiata from Chile) sawdust. Both preparation and characterization of feedstocks, raw/torrefied woods and pine sawdust, were respectively reported by Gouws et al [31] and Moore et al [46]. A summary of the proximate and ultimate analyses of the different woody biomass samples is shown in Table 2, whereas the compositional analysis (required as input parameters to the model) is provided in Table 3.…”

“…Three different pyrolysis reactors (Fig. 1) were considered where the pyrolysis process was conducted on 3 different scales: (1) a µg-scale micropyrolyzer (Multi-shot pyrolyzer) with micro-furnace system (details in Section 2.3.1), (2) a mg-scale micropyrolyser (Horizontal micropyrolyzer) (details in Carrier et al [47]) and (3) a g-scale highpressure pyrolyzer (details in Gouws et al [31]). Further details on the dimensions and operating conditions of these reactors are provided in Table 8.…”

“…Compositional analysis of different woody biomass samples in wt.% (d.a.f.) adapted from Moore et al [46] and Gouws et al [31]. For the hemicelluloses, the LMWCs (LMWC HCE ) decompose via two different pathways: fragmentation (reaction 8), which is the dominant pathway where low molecular weight volatiles, including short-chained acids and non-condensable gases are produced [52], and a char-forming pathway (reaction 9), which becomes more significant at lower temperatures.…”

“…In contrast, during slow pyrolysis in the high-pressure pyrolyzer, the long vapour residence time (19.1 s) and high reactor pressures (15 and 30 bar) resulted in both liquid-phase and gas-phase secondary reactions, which was evidenced by the detection of a large number of secondary products [31]. Therefore, successive secondary liquid-and gas-phase…”

“…Moreover, during slow pyrolysis the heating period is sufficiently low for the reactions to reach equilibrium, but this is not the case during fast pyrolysis [29]. The vapour residence time, pressure and time--temperature history to which the primary volatiles are subjected also plays a significant role in the extent of homogeneous and heterogeneous secondary reactions (and therefore product yield and composition) [30,31]. Semi-global models therefore need to be adapted by keeping in mind the reactor configuration and operating conditions.…”