Effect of biomass high-frequency pre-treatment on combustion characteristics

Combustion characteristics of microwave (2.45 GHz) pre-treated biomass (wood) pellets were studied experimentally to determine the effect of pellets pre-treatment on the biomass composition and the feasibility of their thermo-chemical conversion. A complex study of the main combustion characteristics of the pre-treated biomass samples was carried out using a thermogravimetric method and a pilot-scale combustion test facility. The low-temperature microwave pre-treatment of wood pellets enriched the biomass carbon content from 50 to 60% for biomass pre-treated for 180 sec accompanied by the increasing higher heating values from 19.9 up to 23.4 MJ/kg. The microwave pre-treatment promoted a faster thermal decomposition of biomass pellets with an enhanced heat energy production (≤ 30%) and a correlating increase of the volume fraction of CO₂ in the products up to 25-28%, while the mass fraction of the main volatiles (CO and H₂) in the products decreased, indicating a more complete combustion of the volatiles. The shear of the char combustion stage increased with the increasing pre-treatment time. The data of thermo-gravimetric analysis coincided with the results of the pilot-scale tests. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (Prague, Czech Republic 8/25-29/2012).