基于烘焙过程分析，建立了生物质烘焙处理的能量平衡计算方法，结合固定床烘焙实验结果，研究了烘焙温度和保温时间对杨树枝烘焙特性、烘焙所需热及3种烘焙产物能量分布的影响，探讨了杨树枝烘焙处理的能量平衡. 结果表明，烘焙温度是影响生物炭得率、热值和能量分布的主要因素，随烘焙温度提高，杨树枝炭得率显著降低，液体产物和气体产物逐渐增加，杨树枝炭和不凝气体产物的热值显著增加，而液体产物热值变化不大. 烘焙产物中，杨树枝炭的能量显著高于液体和气体的能量. 随烘焙温度升高，杨树枝烘焙的能量平衡率先快速升高后趋于平稳，在温度225℃、保温时间30 min的条件下，烘焙可获得64.0%的杨树枝炭，能量平衡率约为2.5，烘焙所得液体和气体产物的燃烧热完全能满足杨树枝烘焙能量自给的需要.
Calculation method of energy balance during biomass torrefaction was established based on the analysis of biomass torrefaction process. According to the results of polar branch (PB) torrefaction in a fixed bed reactor, the effect of torrefaction temperature and holding time on characteristics of torrefied products (PB biochar, liquid product and gaseous product), heat requirement and energy distribution during torrefaction were studied. The energy balance of PB torrefaction was also discussed. The results indicated that torrefaction temperature was a key influence factor on biochar mass yield, heating value and energy distribution. The mass yield of PB biochar decreased significantly and mass yields of liquid and gaseous products increased gradually with increasing torrefaction temperature. At the same time, the heating values of PB biochar and gaseous product increased, and the heating value of liquid product had no remarkable change correspondingly. The energy of PB biochar was significant higher than that of liquid and gaseous products. The energy balance ratio of PB torrefaction showed a tendency of increase first and then to be stable with increasing torrefaction temperature. 64.0% of biochar mass yield can be obtained through PB torrefaction at the temperature of 225℃ and the holding time of 30 min, and the relevant energy balance ratio was 2.5. At this condition, the heat produced from combustion of gaseous and liquid products could completely meet the requirement of energy self-supported during PB torrefaction.
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