Evaluating Pyrolysis of Cypress Tree Residues in a Continuous Thermal Reactor

Pyrolysis is a thermochemical process by which biomass is decomposed by heating in the absence of oxygen and the resulting emitted gases and settled bio-char are used for energy supply. Cypress pruning residues due to their gums content are a good source for pyrolysis. In this study, a reactor equipped with a screw conveyor was built and used for pyrolysis of stems and leaves of cypress tree. Then the effects of temperature and residence time of the reactor on their thermal decompositions was investigated using factorial experiments based on a completely randomized design. In these experiments, temperature was set at 5 levels from 300 to 500°C, with 50 degrees intervals and the residence time was set from 5 to 30 minutes with 5 minute intervals. The results showed that, at 1% significant level, both resident time and reactor temperature and their interaction had significant effects on bio-char yields for both stem, and leaves. The analysis of TG/DTG diagrams showed that the bio-char was formed from 200 to 500°C. The highest rate of decomposition of hemicellulose was at 340°C, and it was 450°C and 580°C for cellulose and lignin, selectively. The final rich carbon content of bio-char was formed after 750°C which resulted 23% for the stems and 28% for the leaves. The pyrolysis experiments with different retention time in the reactor indicated that, in general, the amount of bio-char decreases as the retention time increased.