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 (TMAX = 1110 °C) and the kinetic parameters (temperature front velocity vt = 7.9 mm/min, combustion front velocity vc = 8 mm/min, mass loss rate vm = 14.7 g/min) of the process were very similar to those obtained for good-quality hardwood pellets (TMAX = 1090 °C, vt = 5.4 mm/min, vc = 5.2 mm/min, vm = 13.2 g/min) and generally very different form SH (TMAX = 840 °C, vt = 20.7 mm/min, vc = 19 mm/min, vm = 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 (Fout = 0.083 kg/s·m2 for SHP and 0.077 kg/s·m2 for HP) and power output density (Pρ = MW/m2 for SHP and 1.5 MW/m2 for HP).