Effects of biomass blending ratios on flame temperature, alkali concentrations and slagging degree in coal and cornstalk/pine mixed combustion

High contents of sodium (Na) and potassium (K) released from biomass fuels can cause slagging of the incinerator during the co-combustion of coal and biomass fuels. The temperature distributions, Na and K concentrations and slagging index of coal, cornstalk and pine mixed combustion were measured by spectrometer and complementary metal-oxide-semiconductor (CMOS) camera at different blending ratios. The average flame temperature at 2.6 s (1527.82 K) of pine was 1.07 times that at 2.8 s of cornstalk, due to the higher volatile content (75.31 %) of pine compared with cornstalk (53.35 %). As an increase of the blending ratios of cornstalk in the fuel from 20 % to 80 %, the total combustion duration first increased from 40 s to 45 s and finally reduced to 29 s. The nonlinear variation was attributed to the low heating value and low density of cornstalk. Na and K concentrations were positively correlated with the variation in the blending ratios of pine in the fuel. As the blending ratio of cornstalk in the fuel was 40 %, the slagging index was 0.5 (high level of slagging). The slagging degree during the mixed combustion of coal and cornstalk was affected by ash content and Na and K concentrations.