Estimation of the heat required for intermediate pyrolysis of biomass

Abstract

Biomass waste contains an abundant source of energy that can be transformed into high-calorific fuel during intermediate pyrolysis, consequently reducing the use of fossil fuel resources. In the present study, medium density fibreboard (MDF), brewery spent grains (BSG) and post-extraction soybean meal (SM) were used to pyrolysis. Valorisation of these wastes via intermediate pyrolysis was carried out at a temperature of 773 K in a fixed-bed reactor under nitrogen atmosphere. The ultimate analysis showed that MDF char has offered the highest carbon content. Generally, chars obtained from these feedstocks were characterized by different internal microstructures. On the one hand, the surface of MDF char has exhibited pores with a regular pattern of small perpendicular blocks. On the other hand, irregular open spaces were detected in BSG and SM chars. The results of this investigation of the microstructure proved that the studied biomass wastes are perspective feedstocks to obtain high-value bioenergy products. Based on the enthalpy balance, it was concluded that the heating value of the pyrolysis gas was higher, the more endothermic pyrolysis process. The research hypothesis confirms that the higher the K2O/CaO ratio in the ash, the better biomass pyrolysis process was catalysed and as a result, less additional heat was required for pyrolysis. To carry out the pyrolysis of MDF, SM and BSG, additional heat input was required in the amount of 2016.8, 1467.9 and 881.1 kJ, respectively. It was found that 4–10% of the higher heating value of the raw materials was missing to achieve the self-sustaining energy of intermediate pyrolysis.Graphical abstract