麦秆湿解反应水溶液循环对固形产物的影响

Effects of Water Recirculation on Characteristics of Solid Products from Hydrothermal Treated Wheat Straw

为了减少生物质湿解过程的排放和水的消耗,以麦秆为原料,麦秆湿解水溶液为溶剂,在高温高压反应釜中,进行了反应温度为220℃,停留时间为120 min条件下的水循环湿解实验研究,并结合X射线衍射(XRD)、傅里叶红外光谱(FTIR)和热重分析仪的检测分析结果对使用循环水作为溶剂时的麦秆湿解固体产物的微晶结构、化学组成和热稳定性进行了深入分析。研究发现,随水循环次数的增加,固体产物产率和固碳率逐渐增加,同使用新鲜水的麦秆湿解实验相比较,水循环第6次时,固体产物产率和固碳率分别增加至78.7%和92.4%;麦秆湿解固体的有序化程度亦随水循环次数的增加而增加,微晶结构接近于石墨化的程度逐渐提高,有机官能团和脂肪族结构逐渐减少,芳香化和炭化程度逐渐提高;热重分析表明,麦秆湿解固体热稳定性较好,并随水循环次数的增加,热稳定性逐渐增强。麦秆湿解反应水溶液循环利用有益于固体目标产物的生成,并可改善产物的理化特性。

Hydrothermal treatment （HTY） of biomass is a technique which using hot, pressurized water to convert biomass for yielding a solid, coal-like product. Therefore, the treatment and utilization of HTT liquid products has a key effect on its commercial application. This current research work mainly focuses on the effects of products on characteristic from HTF which using recycled process water for multiple process cycles. The hydrothermal experiments were carried out in an autoclave using wheat-straw as raw materials at temperature 220℃ for residence time 120 min with a 30：1 water and biomass mass ratio. The micro-structure, chemical composition and thermal stability of solid products were characterized by using X-ray diffraction （XRD）, Fourier transform infrared （FTIR） and Thermogravimetric analyzer （TGA） with differential scanning calorimetry （DSC）. The results show that with successive recycling, the mass yield and sequestering carbon rate in the solid gradually increased. Compared with the initial HTT, mass yield and sequestering carbon rate after six recycles rose to 78.7% and 92.4%. Upon increasing recycling, the level of structural order in the solid increased, which suggested that the solid tended to further aromatize/graphitize. At the same time, the functional group and aliphatic structure decreased. The TGA analysis results indicated that the thermal stability of solid also increased as the number of cycles increased. Water recirculation during hydrothermal treatment of wheat straw could increase the HTT solid yields and improve their physical and chemical characteristics.