烘焙温度和停留时间对生物炭特性的影响

Influence of Torrefaction Temperature and Residence Time on Biochar Characteristics During Biomass Torrefaction

以杨树枝、柳树枝、稻壳、玉米秸秆、成型稻壳和成型木屑6种生物质为对象,在烘焙温度为200~300℃和停留时间为20~40 min的条件下,利用固定床烘焙实验装置开展了生物质烘焙实验,结合生物炭的工业分析、元素分析和热值测定结果,分析了烘焙温度和停留时间对生物炭H/C,O/C,能量得率,能量密度的影响。结果表明:随着烘焙温度和停留时间的增加,生物炭的挥发分,质量得率,H/C,O/C,能量得率不断下降,固定碳、低位发热量和能量密度不断升高;烘焙温度对生物炭的影响显著强于停留时间,烘焙处理对木质类和农业类生物质影响显著强于成型生物质;在烘焙温度为300℃和停留时间为40 min的条件下,成型生物质的能量密度最高仅为1.10,而木质类生物质的能量密度最高可达到1.40。

Torrefaction experiments of six biomass including polar branch,willow branch, rice husk,corn stalk,pelletized rice husk and pelletized sawdust are investigated in a fixed-bed reactor at the temperature of 200 ～ 300 ℃ and the residence time of 20 ～ 40 min. The variation of H/C ratio,O/C ratio,energy yield,energy density of biochars are analyzed based on the results of proximate analysis,ultimate analysis and low heating value. The obtained results indicate that volatile matter,mass yield,H/C ratio,O/C ratio and energy yield decease,but the fixed carbon, low heating value and energy density increase with the increase of torrefaction temperature and residence time. The influence of torrefaction temperatureon biochar is significantly better than that of residence time,and torrefaction has a significant effect on woody and agricultural biomass compared with pelletized biomass. The energy density of pelletized biomass is only 1. 10,but the energy density of woody biomass is 1. 40 at the temperature of 300 ℃ and the residence time of 40 min.