Study on the Biochar Yield and Heat Required during Pyrolysis of Two-Phase Olive Mill Waste

The present study analyzes the effect of several operating factors (initial sample mass, heating rate, conditions of the crucible, and inorganic matter content) on the pyrolysis of two-phase olive mill waste. Simultaneous TGA-DSC measurements were performed according to a one-half fractional factorial design to obtain statistically significant conclusions. The results from this screening design pointed out that the behavior of the TPOMW pyrolysis process is statistically affected to a greater or lesser extent by the four factors analyzed. The factors related to the promotion of secondary charring reactions (the initial sample mass and the conditions of the crucible) had the main influence on both the apparent heat and charcoal yield. The enhancement of the charring reactions implies a dramatic decrease in the apparent heat of pyrolysis from highly endothermic (2559 +/- 100 kJ kg(-1)) to slightly exothermic (-44.2 +/- 49 kJ kg(-1)). On the other hand, a new approach for modeling the apparent kinetics of TPOMW pyrolysis (both primary decomposition and secondary charcoal production) is proposed. The performance of this approach is good enough to provide satisfactory estimations of a large number of unknown kinetic parameters in very short computational times.