Effects of Temperature and Mg-Based Additives on Properties of Cotton Stalk Torrefaction Products
2018
Zeng, Kuo | Yang, Qing | Che, Qinfeng | Zhang, Yang | Wang, Xianhua | Yang, Haiping | He, Xiao | Wright, Sebastian | Chen, Hanping
In a new development, Mg-based additives were introduced to the process of torrefaction of cotton stalk to enhance the deoxygenation effect. The properties of torrefaction products obtained using temperatures in the range 200–350 °C and three different types of Mg-based additives (MgO, MgO-K₂CO₃, and MgO-KNO₃-NaNO₃) with varied mass ratios (0.5, 1, and 2) were characterized. The yield of solid product significantly declined from 92.02% to 36.95% when the torrefaction temperature rose from 200 to 350 °C, while gas and liquid yields increased to 24.90% and 38.15%, respectively. MgO-K₂CO₃ was the most effective additive because it not only promoted deoxygenation in the solid product (oxygen content decreased by about 43%) but also reduced the loss of hydrogen. CO₂ was the main gas component, and production was promoted as the Mg-based additive mass ratio rose from 0.5 to 2. The phenol and ketone content in the liquid product significantly increased, while the acid content decreased. Biomass torrefaction with Mg-based additives not only produced a low oxygen content solid product but also improved the properties of the byproducts (gas and liquid) so that they could be recovered and utilized as fuel or chemicals.
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