Co-Pyrolysis Characteristics of Torrefied Pine Sawdust with Different Rank Coals

Torrefaction of sawdust has the advantages of increasing its heating value, lowering its O/C ratio, and making it more convenient to transport and crush. Torrefied sawdust has characteristics that are more similar to coal than to sawdust. The initial pyrolysis temperature and residue content of torrefied sawdust are higher than those of sawdust. With the increase of coalification degree of three different coals, the initial pyrolysis temperature and residue contents are raised. The initial pyrolysis temperatures and remaining contents of lignite, bituminous coal, and anthracite are 330, 380, and 500 °C and 61.3, 75.1, and 89.5%, respectively. The torrefied sawdust also has a synergistic effect on the conversion of anthracite and bituminous coal, but it has an inhibitory effect on lignite. The composition of gaseous products was also measured after pyrolysis. The results demonstrate that with the addition of torrefied sawdust to anthracite and bituminous coal, the gaseous products contain more combustible components, such as H2, CO, and CH4, which increase the heating value. Moreover, the effect is more obvious with the co-pyrolysis of torrefied sawdust and anthracite. However, the co-pyrolysis of torrefied sawdust and lignite leads to decreasing CO and light hydrocarbons (CnHm (n=1, 2)) in the resulting gaseous products, which has a negative effect on the quality of the gaseous products. The co-pyrolysis characteristics of torrefied sawdust with different rank coals are discussed in this paper.