The effect of microwave pre-processing of straw pellets on the thermal decomposition of biomass mixtures

Thermal decomposition of biomass mixtures has been experimentally studied to assess the potential for more intensive use of local bioenergy resources (straw) in heat production by co-firing straw with wood or peat pellets and for process control using microwave (MW) pre-treatment of straw pellets. It was found that microwave pre-treatment of straw pellets provides modification of their structure, elemental and chemical composition, increases the porosity of pellets and the heating values of the pellets with partial decomposition of the main components of lignocellulosic pellets, i.e., hemicelluloses, cellulose and lignin. Besides, microwave pre-treatment of straw pellets activates the thermal interaction between the activated pellets of straw and unpre-treated pellets of the mixture that results in faster thermal decomposition and faster release of combustible volatiles (CO, H₂, C_xH_y). The time required for thermal decomposition of biomass mixtures decreases by about 300 s, the average weight loss rate of activated mixtures increases by about 17-20 %, increasing the yield of combustible volatiles by about 24 %.