Comparative Analysis of Pelletized and Unpelletized Sunflower Husks Combustion Process in a Batch-Type Reactor

This paper describes characteristics of the combustion of sunflower husk (SH), sunflower husk pellets (SHP), and, for comparison, hardwood pellets (HP). The experiments were carried out using a laboratory-scale combustion reactor. A proximate analysis showed that the material may constitute an alternative fuel, with a relatively high heating value (HHV) of 18 MJ/kg. For SHP, both the maximum combustion temperatures (T_MAX = 1110 °C) and the kinetic parameters (temperature front velocity v_t = 7.9 mm/min, combustion front velocity v_c = 8 mm/min, mass loss rate v_m = 14.7 g/min) of the process were very similar to those obtained for good-quality hardwood pellets (T_MAX = 1090 °C, v_t = 5.4 mm/min, v_c = 5.2 mm/min, v_m = 13.2 g/min) and generally very different form SH (T_MAX = 840 °C, v_t = 20.7 mm/min, v_c = 19 mm/min, v_m = 13.1 g/min). The analysis of ash from SH and SHP combustion showed that it has good physicochemical properties (ash melting point temperatures >1500 °C) and is safe for the environment. Furthermore, the research showed that the pelletization of SH transformed a difficult fuel into a high-quality substitute for hardwood pellets, giving a similar fuel consumption density (F_out = 0.083 kg/s·m² for SHP and 0.077 kg/s·m² for HP) and power output density (P_ρ = MW/m² for SHP and 1.5 MW/m² for HP).