Comparative torrefaction behaviors of diverse biomass feedstocks and their application in gasification driven by waste heating from converter vaporization cooling flue

In this work, the torrefaction process of 20 kinds of biomass feedstocks was investigated and the subsequent gasification behaviors at different temperatures were investigated. The results showed that torrefaction effectively upgraded fuel quality by increasing the fixed carbon content, while narrowing the overall H/C and O/C ratios. The gasification tests of torrefied biomass were conducted on a thermogravimetric analyzer, and the key parameters of Tmax and DTGmax significantly increased to 780–920℃ and 0.25–0.40%/℃, respectively, suggesting enhanced char reactivity. According to the correlation analysis, it was found that the standard deviations of various parameters for woody biomass decreased, leading to enhanced gasification uniformity, which were higher than those of straw and shell biomass. A validation experiment was performed on a drop tube reactor using waste heat in converter vaporization flue, and torrefied eucalyptus wood showed the best performance at torrefaction and gasification temperatures of 290℃ and 1000℃, respectively, with CO concentration reaching to 25%, higher than that at 260℃ (18%) and 320℃ (23%). Furthermore, the growth rate of combustible gas, the reduction rate of CO2 as well as the lower heating value of syngas reached 36.95%, 24.1%, and 7.53 MJ/Nm3, respectively, demonstrating that moderate torrefaction condition could effectively improve the gasification behavior of biomass.