烘焙条件对生物质烘焙特性的影响

根据生物质种类,选取果实类生物质花生壳、木质类生物质锯末和草本类生物质竹子为对象,考察烘焙条件对生物质特性的影响。利用管式炉为烘焙实验主要装置,结合工业分析仪、元素分析仪等,考察三种生物质在烘焙温度为200 ~ 300℃和时间为30 ~ 90 min条件下烘焙产物的挥发分、固定碳含量、O/C和H/C、质量产率等,并引入烘焙程度指数来衡量烘焙前后的能量变化。实验结果表明：随着烘焙温度的升高,固定碳含量增加到40%以上,挥发分含量减少到50%以下,质量产率也随之下降。烘焙时间的影响弱于烘焙温度,随着烘焙温度的升高,烘焙时间对固体产率的影响逐渐显现,烘焙时间越长,固体产率越低。烘焙温度高于280℃、时间大于60 min时,烘焙后固体的能量产率仅为70%左右。O/C和H/C随烘焙温度升高而降低,草本类生物质竹子的能量产率受温度影响最大。果实类生物质花生壳、木质类生物质锯末的能量产率随烘焙程度指数增大而减小,而草本类生物质竹子的能量产率则呈先增后减的抛物线型,在烘焙程度为0.5时,竹子的能量产率达到最大值。各生物质烘焙程度指数的R²值均大于0.93,因此烘焙程度指数可被视为描述或预测生物质烘焙性能的可行指标。

Effect of Torrefaction Conditions on the Torrefaction Characteristics of Biomass

According to the classification of biomass species, peanut shell (fruit-based biomass), sawdust (woody biomass) and bamboo (herbaceous biomass) were selected to study the effect of torrefaction conditions on the torrefaction characteristics of biomass. Volatiles, fixed carbon, O/C, H/C and solid yield of the three biomass at temperature of 200 ~ 300^oC with the durations of 30 ~ 90 min were investigated by using the tube furnace as the main equipment of the torrefaction experiment, combined with industrial analyzers, elemental analyzers. The torrefaction severity index (TSI) was introduced to measure the energy changes. The experimental results showed that with the increase of temperature, the fixed carbon content increased to more than 40%, the volatile content decreased to below 50%, and the solid yield decreased. The effect of duration time was less important than temperature. As the baking temperature increased, the effect of duration time on the solid yield gradually appeared, and the longer the duration time, the lower the solid yield. When the temperature was higher than 280^oC and the duration time was more than 60 minutes, the solid yield was only about 70%. O/C and H/C decreased with the temperature increased, and herbaceous biomass bamboo was most affected by temperature. The energy yield of fruit-based biomass peanut shell and woody biomass sawdust decreased linearly with the TSI, while herbaceous biomass bamboo was parabolic. When TSI was 0.5, the energy yield of the bamboo reached its maximum. The R² values of TSI were higher than 0.93, so TSI can be considered as a viable indicator for describing or predicting the torrefaction performance of biomass.