麦秆水热炭化水溶液循环对碳及水溶物分布的影响

Effects of water recirculation on distribution of carbon and aqueous products from hydrothermal treated wheat straw

以农业废弃物麦秆为原料,通过水溶液循环利用的水热炭化实验,对麦秆水热炭化过程中碳及水溶有机物主要组分浓度的分布进行了深入研究。结果表明:在220℃、120 min、液固比为30∶1的水热条件下,随水循环次数的增加,水溶产物产率及碳质量分数逐渐减少,水循环第6次以后,水溶产物产率和碳质量分数变化不大,分别约为15%和5%;水溶产物中还原糖、糠醛和5-羟甲基糠醛(5-HMF)的浓度均随循环次数的增加而减少,而乙酸浓度一直呈逐渐增加趋势,并催化了水热炭化反应,水循环第10次时,乙酸浓度达到18.32 g/L。

Using wheat-straw as raw materials,the hydrothermal treatment experiments with recirculation of process water in an autoclave were carried out. The distribution of carbon and major organic components of the aqueous phase were investigated. The results show that,at reaction temperature 220 ℃ for residence time 120 min with water to biomass of 30 ∶1,the mass yield and carbon mass fraction in the aqueous products gradually decreased with water recirculation. However,the value of mass yield and carbon mass fraction remained almost constant and were about 15% and 5% after the 6th recirculation. Hydrothermal process water was very rich carboxylic acid,meanwhile,contained the characteristic functional groups of the aldehydes,ketones,esters and saccharides. As a consequence,with increasing recirculation,the organic functional groups in the aqueous phase declined. Moreover,the concentration of furfural,5-hydroxymethyl-furfural（5-HMF）and reducing sugars sharply declined. In contrast,the concentration of acetic acid increased to 18.32 g/L during recirculation. The acetic acid catalyzed hydrothermal reaction and provoked a decline of aqueous products by water recirculation.