An investigation of pine needles fluidization, combustion performance, and fly ash behavior in fluidized bed combustor

Coniferous forest residue, such as pine needles, has enormous potential in Himalayan territories and could play a significant role in energy supply. The present work, for the first time, investigates the fluidization; combustion performance; and collected fly ash analysis. Experimental results on the cold state show the mixing characteristics of pine needles with silica sand indicate that the 3-mm pine needles with 2% concentration mix well with bed material (silica sand) at fluidization number (FN = 4). The results show that among the four different cases considered for the mixing characteristics of pine needle and silica sand, concentration of pine needles and fluidizing velocity have been employing a substantial impact on the mixing characteristics during fluidization. However, improper mixing was found because of little segregation above and below FN = 4. The combustion studies on pine needles conducted in excessive air atmosphere in FBC had achieved combustion efficiency (η_Combustion) over 73.19%; the temperatures of the dilute phase region were found to higher than the combustion zone, and secondary air pours have no significant effect on flue gas temperature. The results show that the pine needles are easily combusted inside the combustor, and broad work is required for effective usage of a critical portion of pine needles as a feedstock. SEM/EDS analyzes the morphology and compositions of ash and sand. The fly ash elemental heterogeneity is analyzed by using compositional analysis. Finally, the fly ash suggests the evaluation indexes for pine needles with the help of SEM/EDS, elemental analysis and ash fusion temperature. There was no agglomeration found during the period of tests under-considered operating conditions at an average temperature of 817 ºC and received 15–20% unburned carbon in the fly ash sample. Generally, the pine needles characteristics are tremendous valuable source of power and heat. This can provide basal knowledge and may further help the researchers and academics who are working in this area. The present work showed a good agreement to generate future opportunities for using pine needles (forestry litter) in combustion technology.