液固比对生物质水热炭化产物结构演变的影响

INFLUENCE OF LIQUID TO BIOMASS RATIO ON STRUCTURAL EVOLUTION OF PRODUCTS DERIVED FROM BIOMASS HYDROTHERMAL CARBONIZATION

为了研究水量的添加对生物质水热炭化反应过程和目标产物水热焦特性的影响,以草坪草、麦秆和梧桐树叶为原料,利用高温高压反应釜,对3种生物质分别在不同反应温度、液固比(水与生物质原料干基质量比)为10~50的条件下,进行水热炭化实验,并对实验所得水热焦的组成与结构和液体产物中还原糖产量的变化进行分析。研究发现,随着液固比的增加,草坪草、麦秆和梧桐树叶水热焦产率均有所下降,但当液固比超过30以后,变化幅度均不大,在液固比10~50范围内,水热焦产率是液固比的函数,均可用单指数衰减函数进行拟合,这有利于水热焦产率的预测;3种水热焦的碳含量和液体产物中还原糖产量随液固比的增加而增加,而糖类化合物特征峰的红外吸收强度有所减弱;由傅里叶红外光谱分析可知,随着温度的升高及液固比的增加,水热炭化反应的影响逐渐减弱,在反应温度200~240℃,液固比从10增加到50时,主要增加水的溶解性能,对化学反应的影响较小,从水热焦的理化特性演变发现温度较高时,可选择相对较低的液固比。

Water is an essential solvent for hydrothermal carbonization （HTC） of biomass. To investigate the influence ot water quality on reaction process and the characteristics of solid product, the experiments were conducted at water to biomass ratio （based on dry basis mass） of 10 to 50 using lawn grass, wheat straw, and platanus leaves as feedstock. At the same time, to explore the relation between reaction temperature and water： biomass, lawn grass, wheat straw, and platanus leaves were respectively treated at 200,220 and 240 ℃ in a 2 L autoclave during HTC. The results showed that with increasing ratio of water： biomass, the yields of hydrochar from the three feedstocks gradually decline. As the ratio of water to biomass increases to 30, the changes of solid yields are slight. The yields of hydrochar can be fitted by single exponential decay function over the range of the ratios of water ： biomass used. The fitting curve is favorable to predict the yields of hydrochar. The carbon content of hydrochar and the yields of reducing sugar in liquid products enhance with the ratio of water to biomass increased. However, the characteristic peak intensity of sugar compounds becomes weaken. Based on the Fourier transform infrared （FTIR） spectra, as the reaction temperature increases, the effects of the changes of ratio of water to biomass on HTC process begin to decrease. When the ratio of water to biomass increases from 10 to 50, the dissolution reaction is enhanced at 200-240 22 during HTC. According to the evolution of physical and chemical properties of hydrochar, HTC can be carried out at a higher temperature with a relative low ratio of water to biomass.