3. Results and discussion
3.1. Ultimate analysis, proximate analysis and major ash forming
metal content analysis
As shown in Table 2, carbon contents increase and oxygen contents
decrease in the biochars with increasing pyrolysis temperature,
indicating increased energy densities of the biochars. In
contrast, there is no obvious change for nitrogen and sulfur contents
in the biochars with the increasing temperatures and their
values are lower than those of lignite. The lower contents of nitrogen
and sulfur in biochars imply that like raw biomass combustion,
similar environmental benefits can be achieved from the combustion
of the biochars. Fig. 2 shows the removal degrees of carbon
and hydrogen at different temperatures and it is evident that
woody biomass PW underwent lower remove rates of hydrogen
and carbon than non-woody CF at identical pyrolysis conditions.