Correlations to predict elemental compositions and heating value of torrefied biomass

Measurements reported in the literature on ultimate analysis of various types of torrefied woody biomass, comprising 152 data points, have been compiled and empirical correlations are developed to predict the carbon content, hydrogen content, and heating value of a torrefied wood as a function of solid mass yield. The range of torrefaction temperature, residence time and solid yield of the collected data is 200-300°C, 5-60 min and 58-97%, respectively. Two correlations are proposed for carbon content with a coefficient of determination (R²) of 81.52% and 89.86%, two for hydrogen content with R² of 79.01% and 88.45%, and one for higher heating value with R² of 92.80%. The root mean square error (RMSE) values of the proposed correlations are 0.037, 0.028, 0.059, 0.043 and 0.023, respectively. The predictability of the proposed relations is examined with an additional set of experimental data and compared with the existing correlations in the literature. The new correlations can be used as a useful tool when designing torrefaction plants, furnaces, or gasifiers operating on torrefied wood.